Why a “conservative” number in multifamily underwriting quietly becomes the riskiest assumption in the deal.
A 75% break-even occupancy often gets labeled as conservative. The label is comforting. The label is also misleading.
Break-even occupancy answers a real question in multifamily underwriting: how much revenue can a property lose, through vacancy, concessions, or rent decline, before it stops covering its operating expenses and debt service. I have written before about why every apartment investor should know this number for any deal they evaluate.
What I want to address now is the failure pattern hiding inside the comfort.
The number is only as conservative as its inputs
Break-even occupancy is calculated from three moving inputs: operating expenses, debt service, and gross potential revenue. Investors often treat the resulting number as a fixed property characteristic. It is not. It is the output of three assumptions, each exposed to its own pressure.
When the model produces a 75% break-even, it is saying this: under today’s expense load and today’s debt service, the property can absorb 25 percentage points of vacancy or revenue loss before it stops paying for itself.
Change any of those inputs, and the break-even moves. Change all of them at once, and it can shift dramatically while the property is sitting still.
The inputs do not move independently
The clean version of stress testing assumes one variable moves at a time: occupancy drops, expenses hold, debt holds. The real-world version is messier. Pressure tends to arrive in clusters.
Consider what has happened in the apartment expense base. Federal Reserve research published in September 2025 found that average multifamily property insurance costs rose from about $39 per unit monthly in 2019 to roughly $68 by 2024 in real terms, an increase exceeding 75%. A Minneapolis Fed survey reached a similar conclusion: by 2024, premiums had roughly doubled compared with 2021, more than six times the pace of consumer price inflation. One operator estimated that over half of all operating expense inflation since 2020 traced back to property insurance alone.
CBRE has noted that although insurance represents only about 8% of total multifamily operating expenses, it has driven roughly 17% of total expense growth since 2019. The 2024 NAA, IREM, and BOMA Income/Expense IQ benchmarking report flagged property taxes and insurance as the most disruptive and volatile expense lines in the asset class, with total operating expenses averaging approximately $8,657 per unit.
These are not isolated stories. They describe a system in which several expense lines moved in the same direction at the same time. Insurance reset. Property taxes adjusted at reassessment. Payroll inflation embedded into operating budgets. Repair and maintenance followed materials inflation. For floating-rate borrowers, debt service moved with the rate cycle.
Each of those individually would shift break-even by a point or two. Stacked, they can move it by five, eight, or more.
What the metric leaves out entirely
Then there is what the formula does not capture in the first place. Break-even occupancy is calculated above the line. It accounts for operating expenses and debt service. It does not account for capital expenditures, principal amortization on certain loan structures, replacement reserves, or unbudgeted repairs that surface mid-hold.
A property can operate well above its break-even occupancy and still face real financial stress, because the cash demands below the line are real even when the metric does not show them. If CapEx reserves were not raised at acquisition, or if the original budget proves insufficient and unexpected capital needs surface later, those dollars come from operating cash flow or from the next capital call. Either way, the operator is funding them from somewhere the break-even calculation never asked about.
The metric assumes timing alignment that does not exist
Most underwriting models are built on annualized assumptions. Real estate does not operate on annual cadence. Cash comes in when tenants pay. Cash goes out when expenses demand it. The two rarely move in sync.
A large turn cycle can hit before leasing stabilizes. A tax reassessment can land before rent increases take effect. Deferred maintenance can surface all at once. Break-even occupancy assumes smooth alignment across the year. Reality delivers compression. When multiple cash demands arrive before revenue catches up, the annualized metric becomes irrelevant for the question that actually matters: whether the property can meet its obligations this month.
The failure pattern
Here is how the failure pattern typically unfolds. The deal is underwritten with a 75% break-even and labeled conservative on that basis. Insurance renews 30% to 50% above the model. Property taxes step up at the next reassessment cycle. Payroll runs 8% to 12% above plan. The rate cap on the bridge loan expires, and replacement is materially more expensive. CapEx surfaces ahead of schedule. By the time someone runs an updated calculation, break-even has moved closer to 85%, and the operator is also funding capital needs the metric never tracked.
The market has not collapsed. Occupancy has not fallen off a cliff. The property is still recognizably the same asset. But the cushion that justified the original underwriting has been consumed quietly, line by line, before any of the headline risks even arrived.
That is the moment when break-even occupancy stops being a safety metric and starts being a leading indicator of distress.
A more useful question
The metric itself is not the problem. The framing is.
Break-even occupancy is genuinely useful when it is treated as a current snapshot of a moving target, with explicit acknowledgment of what it does not capture. It becomes dangerous when it is treated as a fixed property attribute that bakes in a margin of safety.
The better questions sound like this. Where does break-even land if insurance resets at the next renewal and stays there. Where does it land after a property tax reassessment. What capital demands sit below the line, and are reserves sized to absorb them. Can the property meet its obligations in months when revenue lags expenses, not just on an annual average.
The answer to those questions is the actual safety margin. The single number on the underwriting page is just the starting point.
Closing thought
A 75% break-even means little if the inputs that produced it cannot survive 24 months without revision, if the formula ignores the capital calls coming due, or if the cash flow rhythm does not match the expense rhythm. A higher break-even built on stress-tested inputs, fully reserved capital, and timing-aware cash modeling is a more honest number than a lower one built on inputs untouched since the offering memorandum.
The discipline is not in finding properties with low break-even occupancy. The discipline is in pressure-testing the metric for what it captures, what it excludes, and when it lies.
Vessi Kapoulian
Breaking down multifamily underwriting one step at a time to create educated and empowered investors
P.S. If you would like a second set of eyes on a deal or want to sharpen your underwriting through a risk lens, feel free to connect with me.
P.P.S. And if you want to go deeper into analyzing multifamily investments step-by-step, my book and the Mastering Multifamily Underwriting program walk through this process in plain English, from acquisition to exit.
Sources
- Hughes, Samuel K., and Raven Molloy. “Rising Property Insurance Costs and Pass-Through to Rents for Apartment Buildings.” FEDS Notes, Federal Reserve Board of Governors, September 19, 2025.
- Federal Reserve Bank of Minneapolis. “Rising Property Insurance Costs Stress Multifamily Housing.” 2025.
- CBRE. “Insurance Costs Suppress Multifamily Values Most in Certain Sun Belt Markets.” 2024.
- National Apartment Association, IREM, and BOMA. 2024 Income/Expense IQ Benchmarking Report. Published August 2025.