Pro forma assumptions are where a seller's optimism gets quantified, and the buyer's job is to take that document apart and rebuild it. A pro forma is a multi-year projection of income, expenses, and cash flow under a chosen set of assumptions, and every one of those choices was made by someone who wants the deal to look good. The math is rarely wrong. The inputs are the argument. An underwriter who accepts the seller's assumptions is not underwriting the deal, they are underwriting the broker's marketing. Five assumptions carry almost all of the optimism, and each one should be challenged before a number is trusted.
Key Takeaways
A pro forma is only as honest as its assumptions, and the arithmetic almost never fails. The inputs are where the optimism lives.
Rent growth is the first flag: seller convention often runs 3% every year, while disciplined buyers model 0% for years one and two, then inflationary.
The exit cap rate is the single most consequential assumption, and a exit cap equal to or below the going-in cap is a red flag for unrealistic optimism.
Prudent practice sets the exit cap at the going-in cap plus 25 to 50 basis points for a five-year hold, per FNRP, to account for an aging asset.
Expense growth, vacancy, and capital reserves are the quiet three: understating any of them inflates net operating income and hides real cost.
Why Should Buyers Distrust a Seller's Pro Forma Assumptions?
Buyers should distrust a seller's pro forma assumptions because the document is built to present the deal at its most favorable, and every assumption bends toward that goal. The seller's broker is not lying, they are showing the optimistic version because that is their job. The buyer's job is the opposite: strip the pro forma apart and rebuild it with independent assumptions.
The reason this matters so much is compounding. A pro forma projects five, seven, or ten years forward, and a small optimistic bias in an annual assumption compounds into a large distortion at exit. A 3% rent growth assumption versus a 0% assumption for the first two years does not sound like much, but carried across a five-year hold and capitalized at exit, the difference reshapes the entire return. As the operator's rule goes, the seller's pro forma is a hypothesis, and the buyer who does not test it is buying the hypothesis at full price.
What Are the Five Pro Forma Assumptions Buyers Should Always Challenge?
The five assumptions that carry the most optimism are rent growth, the exit cap rate, expense growth, vacancy, and capital reserves. Each one, when nudged in the seller's favor, inflates projected net operating income or the exit value, and each is challengeable against a defensible convention rather than the seller's chosen number.
Here is the buyer's counter-convention for each, drawn from FNRP and Thesis Driven underwriting guidance:
Assumption | Seller convention | Disciplined buyer convention |
Rent growth | ~3% every year, or inflationary throughout | 0% years 1-2, then inflationary (~2-3%) |
Exit cap rate | Equal to going-in, or 25 bps higher as a token | Going-in + 25 to 50 bps for a 5-year hold |
Expense growth | 2%, often below actual cost inflation | 3%+, matched to recent expense trends |
Vacancy | Optimistic stabilized figure | Submarket actual, plus a stress case |
Capital reserves | Thin or omitted | Per-unit reserve appropriate to asset age |
Rent growth is the first flag. Seller convention runs roughly 3% per year or inflationary throughout the hold, while disciplined buyers model 0% for the first year or two, then inflationary thereafter, on the logic that near-term rent gains are uncertain and should be earned, not assumed. The gap between those two paths, compounded across a five-year hold, materially changes the exit valuation.
Expense growth, vacancy, and capital reserves are the quiet three. A seller who grows expenses at 2% while inflation and the National Apartment Association's reported cost trends run higher is understating go-forward cost. National Apartment Association data shows repairs and maintenance up 3.7% year over year in 2024, so a 2% expense escalator is optimism disguised as arithmetic. Thin or omitted replacement reserves inflate near-term net operating income by deferring capital that the asset will demand anyway.
Why Is the Exit Cap Rate the Assumption That Matters Most?
The exit cap rate matters most because it capitalizes the entire terminal value, so a small change in it swings the projected sale price and the return more than any operating assumption. It is also the assumption sellers most often abuse, typically setting the exit cap rate equal to the going-in cap, sometimes nudged 25 basis points higher as a token gesture toward conservatism.
That convention ignores a basic reality: the asset is older at exit than at purchase, and an older asset in a normal market commands a higher cap rate, meaning a lower price per dollar of income. Setting the exit cap equal to or below the going-in cap rate is flagged as a red-flag assumption indicating unrealistic optimism. FNRP's guidance is to set the exit cap at the going-in cap plus 25 to 50 basis points for a five-year hold, and plus 50 to 75 basis points for a seven-to-ten-year hold.
The sensitivity is not subtle. Take a stabilized net operating income of $1,800,000. At a 5.5% exit cap, the terminal value is $1,800,000 divided by 0.055, or about $32.7 million. Move the exit cap to 6.0%, a 50-basis-point shift, and the terminal value falls to $1,800,000 divided by 0.060, or $30.0 million. That single half-point assumption is worth roughly $2.7 million of exit value.
Exit cap rate | Terminal value on $1.8M NOI |
5.50% (going-in, seller convention) | ~$32,700,000 |
5.75% (going-in + 25 bps) | ~$31,300,000 |
6.00% (going-in + 50 bps) | ~$30,000,000 |
The takeaway is that the exit cap deserves the most scrutiny precisely because it does the most work. Rent growth optimism plays out over years of operations. The exit cap converts a single assumption into millions of dollars of value in one line, which is why it matters more than the rent growth it is often paired with.
Frequently Asked Questions
What is a pro forma in commercial real estate? A pro forma is a multi-year projection of a property's income, operating expenses, debt service, and cash flow under a chosen set of assumptions about rents, vacancy, expense growth, and exit. It is an argument about the future, not a record of the past.
What is a red flag exit cap rate assumption? An exit cap rate equal to or lower than the going-in cap rate is a red flag, because it implies the asset will sell at a higher price per dollar of income despite being older. Disciplined underwriting sets the exit cap above the going-in cap.
What rent growth should a buyer assume in a pro forma? Disciplined buyers commonly assume 0% rent growth for the first one or two years, then inflationary growth of roughly 2 to 3% thereafter. This contrasts with the seller convention of assuming 3% or inflationary growth from year one, which front-loads uncertain gains.
Conclusion
A pro forma is not a forecast, it is a set of choices, and the buyer who accepts those choices inherits the seller's optimism at full price. The arithmetic in these models is almost always correct. The assumptions underneath it are where the deal is made to look better than it is, and five of them, rent growth, exit cap rate, expense growth, vacancy, and reserves, carry nearly all of that optimism.
The operators who underwrite well take the seller's pro forma apart and rebuild it with their own conventions: rent growth earned rather than assumed, an exit cap that respects an aging asset, expense growth matched to real cost inflation, and reserves the asset will actually need. The goal is not pessimism. The goal is a projection the buyer can defend after closing, when the assumptions become results.