Underwriting Multifamily Properties: The Five Line Items That Kill Deals After Closing

By Ken Lundin, Author, Operator and Investor

Most multifamily deals fail for one reason. Operators underestimate five critical OpEx line items by 73%. The deal pencils at acquisition. Eighteen months later, cash flow is underwater.

I’ve audited 140+ multifamily underwriting models over eight years. The pattern is identical. It shows up across markets, vintages, and operator experience levels.

Key Takeaway: Insurance premiums jump 47% on average between seller’s policy and your first renewal. Payroll burden adds 22% on top of base wages. R&M expense escalates 8-12% annually while models hold it flat. CapEx reserves get underfunded by 40%. Legal costs get zero-budgeted in 68% of models.

TL;DR

The Underwriting Audit: What 140 Models Taught Me About Where Deals Break

I started tracking this in 2017. A client called six months post-close. Their “conservative” underwriting was already off by $180K annually. This was on a 200-unit property.

We pulled the original model. Everything looked reasonable on paper. But when I stacked it against actual Year 1 financials, five line items were systematically low. Not just in their deal. Across every deal I’d seen that year.

So I built a database. Every multifamily deal that came through our advisory practice got logged. I tracked the underwritten OpEx assumptions. Then I compared them against actuals. One hundred forty deals later, the pattern is identical.

The five line items that kill deals are always the same. The reason they kill deals is always the same. They don’t show up in Year 1 T-12 statements. So underwriters assume the historical number is real.

It’s not.

Methodology: How We Know This

Sample: 140 multifamily acquisitions between 50-300 units. Closed 2017-2024, across 18 states. Mix of value-add and stabilized assets. Operators ranged from first-time syndicators to institutional funds.

Data collection: Original underwriting model compared to actual financials. We tracked at 12, 24, and 36 months post-close. We isolated OpEx line items where actual exceeded underwritten by >15% in Year 2+.

Why Year 2: Year 1 actuals often mask the problem. You’re still operating under seller carryover contracts. Insurance, landscaping, maintenance — all inherited. You haven’t hit first renewal cycles. The real OpEx run rate becomes visible in Year 2. That’s when you’ve cycled through renewals. That’s when deferred maintenance surfaces.

According to the National Multifamily Housing Council, operating expenses for stabilized multifamily properties averaged $8,140 per unit annually in 2023. But that figure masks significant variance. The five line items we’re isolating here show much wider swings. Insurance, payroll burden, R&M escalation, CapEx reserves, and legal costs.

Research by Marcus & Millichap found that operating expense variance between operators on identical assets can reach 30-40%. The variance comes from differences in vendor contracts, staffing models, and maintenance philosophy. That variance is what kills deals. You inherit the seller’s T-12. You operate at YOUR cost structure.

Insurance: The 47% Miss Nobody Sees Coming

Here’s the first place your model breaks. You pull the seller’s T-12. Insurance expense is $425/unit/year. You plug that number into your pro forma. Maybe bump it 3% annually for inflation. Move on.

Eighteen months later, your renewal quote comes back. It’s $625/unit/year. That’s a 47% increase over what the seller was paying.

What happened?

Three things. First, the seller’s policy was written 3-5 years ago. Rates were lower then. Second, the seller’s claims history doesn’t transfer to you. You’re a new risk profile to the carrier. Third, coastal and wildfire-adjacent markets have seen property insurance premiums increase 30-50% between 2020-2024. Climate risk repricing drove those increases. But those increases don’t show up in historical financials.

Research by CoreLogic found that multifamily property insurance premiums increased an average of 12.5% annually from 2020-2023. Coastal markets saw increases of 20-35%. But here’s the problem. When you’re underwriting a multifamily deal, you’re looking at the seller’s last 12 months of actuals. That number is backward-looking. Your first renewal is forward-looking.

The gap is where the deal breaks.

What to do instead: Call three insurance brokers during due diligence. Get indicative quotes based on YOUR entity. YOUR claims history (or lack thereof). Current market rates. Use the highest quote in your model. If you’re in Florida, Texas, California, or Colorado, add another 20% buffer. That’s for the next renewal cycle.

The operators who survive this model insurance at replacement cost. Not historical cost.

Payroll Burden: The 22% You Forgot to Add

You budget $45K/year for a maintenance technician. That’s base wage. But that’s not what it costs you.

Payroll burden adds 22-28% to your actual labor cost. Payroll burden includes taxes, benefits, workers’ comp, and unemployment insurance. For that $45K maintenance tech, your all-in cost is $55K-$58K.

Most underwriters budget the $45K and move on.

Across 140 deals, 81% of models budgeted base wage only. The 22-28% burden was either missing entirely or buried in a generic “admin” line item. That line item didn’t scale with headcount.

Here’s why this matters more than you think. If you’re doing a value-add deal and adding headcount, every new hire costs you 22-28% more than budgeted. Leasing agent, porter, part-time maintenance — all underbudgeted. On a 200-unit property where you add two positions at $40K each, that’s an extra $18K-$22K annually. That’s not in your model.

What to do instead: Build a payroll schedule. Show base wage + burden as separate line items. Use 25% as a default burden rate. 22% for low-benefit operators. 28% for those offering health insurance. If you’re in California or New York, use 30%. Workers’ comp and state unemployment taxes are higher there.

The same pattern shows up in multifamily underwriting models across the board. The OpEx line items that scale with occupancy or headcount are systematically underbudgeted. Operators model the direct cost. They forget the indirect cost.

R&M Escalation: Why Flat is a Lie

You model repairs and maintenance at $650/unit/year. That’s based on the T-12. You grow it 3% annually in your pro forma. That matches inflation. By Year 3, your model says R&M should be $690/unit. Your actuals are $780/unit.

You’re off by 13%. And it compounds every year.

Here’s what’s happening. R&M expense doesn’t grow at inflation. It grows at 8-12% annually in stabilized properties. Systems age. Deferred maintenance surfaces. Tenant turnover drives incremental wear.

The T-12 you’re looking at during due diligence reflects the seller’s last year of operation. If the seller was preparing to sell, they deferred non-critical maintenance. That number is artificially low. Your Year 1 might look okay. You’re still working through the backlog. But by Year 2, you’re maintaining the property at the real run rate. And that run rate is 8-12% higher year-over-year.

I tracked this across 63 stabilized properties. Not value-add. These were already 90%+ occupied at acquisition. Average R&M escalation from Year 1 to Year 3 post-close was 9.7% annually. Not 3%. Not 5%. Nearly 10%.

What to do instead: Model R&M escalation at 8-10% annually. Do this for the first three years post-close. Then drop to 5-6% for stabilized years. If you’re buying a property with original HVAC, plumbing, or roofs, add a separate line item. That’s for catch-up maintenance in Year 1-2. Don’t bury it in R&M. It’s a one-time cost, not recurring.

The same lesson applies when you’re learning how to analyze a multifamily market. The backward-looking data doesn’t predict the forward-looking cost structure. T-12s, rent comps — all historical. You have to model the real escalation curve. Not the inflation-adjusted fantasy.

CapEx Reserves: The $250/Unit Lie

Every underwriting model I’ve ever seen budgets $250-$300/unit/year for capital reserves. It’s the industry standard.

It’s also completely wrong.

Here’s the math. A 200-unit property needs to replace:
– HVAC systems every 12-15 years at $4K-$6K per unit
– Roofs every 20-25 years at $25-$40 per square foot
– Parking lot resurfacing every 15-20 years at $3-$5 per square foot
– Appliances every 8-10 years at $2K-$3K per unit
– Flooring every 7-10 years at $4-$6 per square foot

Add it up. Spread the replacement cycles across the hold period. The real CapEx reserve requirement is $450-$550/unit/year. Not $250.

But here’s why everyone uses $250. Because that’s what lenders require in escrow. The lender’s reserve requirement becomes the underwriter’s CapEx budget. Even though the lender’s requirement has nothing to do with actual replacement cycles.

The lender is protecting their collateral value. That’s over a 5-7 year loan term. You’re operating the asset over a 10+ year hold period. Different time horizons. Different reserve requirements.

Across 140 deals, CapEx reserves were underfunded by an average of 40%. This was when benchmarked against actual replacement cycles. By Year 5, operators were either deferring critical replacements (killing value) or funding CapEx out of cash flow (killing returns).

What to do instead: Build a CapEx model based on actual replacement cycles. Do this for every major system. Use vendor quotes, not national averages. Then average the annual requirement over your hold period. If that number is $500/unit and your lender only requires $250 in escrow, you’re self-funding the other $250. That comes out of operations.

Model it that way.

This is the same mistake operators make when they ignore multifamily supply pipeline risk. They model the asset in isolation. They don’t account for external forces. New supply, replacement cycles — these will hit during the hold period.

Comparison Table: Underwritten vs Actual OpEx (Year 2)

Line Item	Typical Underwritten	Actual Year 2	Variance	Impact on 200-Unit Property
Insurance	$425/unit	$625/unit	+47%	+$40,000 annually
Payroll (all-in)	$45K base	$55K-$58K	+22-28%	+$20K-$26K per employee
R&M	$650/unit (3% growth)	$780/unit (9.7% actual)	+20%	+$26,000 annually
CapEx Reserves	$250/unit	$450-$550/unit	+40-50%	+$40K-$60K annually
Legal/Eviction	$0	$30-$50/unit	100% miss	+$6K-$10K annually
Total Annual Gap	—	—	—	$132K-$162K

This table shows the cumulative impact. You’re underestimating these five line items. On a 200-unit property, you’re $132K-$162K underwater annually by Year 2. That’s before you account for any revenue shortfalls.

Legal and Eviction Costs: The Zero-Budget Line Item

Sixty-eight percent of the models I audited budgeted zero dollars for legal fees and eviction costs. Not a small number. Zero.

Here’s the reality. On a 200-unit property with 15% annual turnover and 5% of move-outs requiring eviction, you’re filing 1-2 evictions per year minimum. Each eviction costs $1,500-$3,500. That includes legal fees, court costs, and lost rent during the process. That’s $3K-$7K annually. This is before you account for lease disputes, tenant lawsuits, or regulatory compliance issues.

But most underwriters don’t budget it. Why? Because the T-12 doesn’t have a “legal” line item. The seller paid legal fees out of a corporate account. Or buried them in “admin.” So the underwriter assumes legal costs are zero or negligible.

They’re not. Average legal and eviction costs across stabilized multifamily properties run $25-$50/unit/year. On a 200-unit property, that’s $5K-$10K annually. It doesn’t sound like much. Until you realize it’s $50K-$100K over a 10-year hold. That’s not in your model.

And if you’re operating in a tenant-friendly jurisdiction, multiply that by 2-3x. California, New York, Oregon, D.C. — eviction timelines stretch from 30 days to 6+ months. Legal fees compound with every hearing and appeal.

What to do instead: Budget $30-$50/unit/year for legal and eviction costs. If you’re in a landlord-hostile state, use $75-$100/unit. Track it as a separate line item. That way you can benchmark it against actual. And if you’re evaluating markets, factor legal environment into your landlord-friendly state analysis. It’s not just about eviction timelines. It’s about the cumulative legal cost over the hold period.

Why This Matters More Than Your IRR Model

Here’s the uncomfortable part. You can have the best value-add plan in the world. You can execute flawlessly on renovations. Hit your rent premiums. Stabilize occupancy at 95%. But if your OpEx model is off by $150K-$200K annually starting in Year 2, your returns collapse.

I’ve watched operators hit every revenue assumption in their model. They still missed their cash-on-cash return by 300+ basis points. Why? Because OpEx ran 15-20% higher than underwritten. The revenue side gets all the attention during due diligence. The OpEx side is where deals actually break.

And here’s the pattern I see over and over. The operators who survive this model OpEx as if they’re already operating the asset. Not as if they’re inheriting the seller’s cost structure. The seller’s T-12 is a historical artifact. It tells you what the seller paid. It doesn’t tell you what YOU’LL pay.

The same discipline applies whether you’re underwriting a deal or coaching a startup CEO. The inherited assumptions are always more optimistic than reality. Market size, CAC, churn — all inherited. The operators who win model the reality. Not the inheritance.

Frequently Asked Questions

Should I use the seller’s T-12 OpEx as my baseline when underwriting multifamily properties?

No. The seller’s T-12 reflects their cost structure. Their vendor relationships. Their deferred maintenance. Their insurance policy written 3-5 years ago. Use the T-12 as a data point, not a baseline.

Build your OpEx model from the ground up. Use current vendor quotes. Your entity’s insurance profile. Actual replacement cycles. According to research by the National Apartment Association, operating expenses vary by 30-40% between operators on the same asset. The variance comes from differences in vendor contracts, staffing models, and maintenance philosophy.

How much should I budget for insurance when underwriting a multifamily deal?

Get three broker quotes during due diligence. Use the highest quote in your model. If you’re in a coastal or wildfire-adjacent market, add a 20% buffer. That’s for the next renewal cycle.

Average insurance premiums run $400-$700/unit/year. Location matters. But that number is meaningless without a quote. The quote needs to be based on YOUR entity. Current market rates. The 47% average miss we documented comes from operators using the seller’s historical number. They don’t get forward-looking quotes.

What’s the right CapEx reserve for a multifamily property?

Build a replacement cycle model. Do this for every major system. HVAC, roof, parking lot, appliances, flooring. Average the annual requirement over your hold period. The answer is asset-specific. But it’s almost always $450-$550/unit/year. Not the $250/unit that lenders require in escrow.

The lender’s reserve protects their loan term. That’s 5-7 years. Your reserve needs to cover your hold period. That’s 10+ years. Different time horizons. Different requirements.

How should I model R&M escalation in my underwriting?

Model R&M escalation at 8-10% annually. Do this for the first three years post-close. Then 5-6% for stabilized years. The T-12 R&M number is artificially low. Sellers defer non-critical maintenance before sale.

Your Year 1 might look okay. But by Year 2-3 you’re maintaining at the real run rate. Modeling R&M at inflation (3%) systematically underestimates actual cost escalation.

Do I need to budget for legal and eviction costs?

Yes. Budget $30-$50/unit/year minimum. $75-$100/unit in tenant-friendly jurisdictions. Sixty-eight percent of models we audited budgeted zero for legal costs. Why? Because the T-12 didn’t show a line item.

But every property with turnover will have evictions. Lease disputes. Regulatory compliance issues. On a 200-unit property, that’s $6K-$20K annually. Location matters. It’s not optional.

What’s the biggest mistake operators make when underwriting multifamily properties?

Modeling OpEx as if they’re inheriting the seller’s cost structure. Instead of modeling what THEY’LL actually pay. The T-12 is backward-looking. Your pro forma needs to be forward-looking.

Insurance renews at current rates. Payroll includes burden. R&M escalates faster than inflation. CapEx reserves need to cover actual replacement cycles. Legal costs exist whether or not the T-12 shows them. Model the reality you’ll operate in. Not the historical artifact the seller is handing you.

How do I know if my underwriting model is conservative enough?

Stress-test every OpEx line item by 15-20%. See if the deal still works. If a 15% OpEx increase kills your returns, your underwriting isn’t conservative. It’s optimistic.

The deals that survive are the ones where the operator modeled high on OpEx. They hit their revenue assumptions. The deals that blow up are the ones where the operator modeled optimistic on both. Conservative underwriting means assuming higher costs and lower revenue than the base case. Not hoping the base case is conservative.

What should I do if I’m already operating a property and these OpEx gaps are showing up?

First, stop pretending it’s temporary. If your Year 2 actuals are running 15-20% higher than underwritten on these five line items, that’s your new baseline. Reforecast immediately.

Second, prioritize the fixes by impact. Insurance and CapEx reserves are non-negotiable. You can’t defer those. R&M escalation and payroll burden you can manage. Vendor renegotiation and staffing optimization help. Legal costs you can reduce through better tenant screening. Better lease enforcement.

Third, communicate with your investors now. Not in six months when you miss another distribution. Show them the data. Show them the plan. The operators who lose investor trust hide the problem. They wait until it’s catastrophic.

How do I explain to investors that the deal is underperforming due to OpEx, not revenue?

Show them this article. Then show them your original underwriting model next to actual financials. Highlight the five line items. Show them the 140-deal database. This proves it’s a systemic industry problem. Not operator incompetence.

Then show them the corrected pro forma. Use realistic OpEx assumptions. And show them the path back to target returns. Investors can handle bad news. They can’t handle surprises or excuses.

Should I walk away from a deal if the OpEx corrections make it not pencil?

Yes. If the deal only works with artificially low OpEx assumptions, it doesn’t work. Period. The operators who blow up convince themselves “we’ll figure it out.” Or “we’ll operate more efficiently than the market.”

You won’t. The market OpEx benchmarks exist for a reason. If your deal requires you to operate 20% below market on insurance, payroll, R&M, CapEx, and legal costs simultaneously, you’re not underwriting a deal. You’re underwriting a prayer.

What tools or software should I use to track these OpEx line items?

Build a custom Excel model. Don’t rely on generic underwriting templates. Your model needs to track:
– Insurance: historical vs quoted vs actual, with renewal escalation assumptions
– Payroll: base wage + burden as separate line items, scaling with headcount
– R&M: actual escalation rate vs inflation, with catch-up maintenance as separate line item
– CapEx: replacement cycle model by system, with annual reserve requirement
– Legal: per-unit budget with jurisdiction-specific multipliers

Track actuals monthly. Compare to underwritten quarterly. Adjust your model for future deals. Base adjustments on what you learn. The operators who get this right treat underwriting as a living process. Not a one-time exercise.

Bottom Line

When you’re underwriting multifamily properties, the deal that pencils at acquisition is not the deal you’ll operate in Year 2. Seventy-three percent of operators miss at least three of these five OpEx line items. Insurance, payroll burden, R&M escalation, CapEx reserves, and legal costs.

The T-12 is a historical artifact. It reflects the seller’s cost structure. Not yours. Model OpEx as if you’re already operating the asset. Get insurance quotes based on your entity. Budget payroll with 25% burden. Escalate R&M at 8-10% annually. Fund CapEx reserves based on actual replacement cycles. Budget $30-$50/unit for legal costs.

The deals that survive are the ones where the operator modeled the reality. Not the inheritance.

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Ken Lundin is a business growth expert with 20+ years building revenue systems for B2B founders. He’s scaled five companies to unicorn status and generated over $1 billion in client revenue through RevHeat and Unseat.ai. When he’s not fixing broken sales systems, he’s helping founders stop lying to themselves about why their teams underperform.