Your Rent Isn't the Lender's Income — Here's the Math They Actually Use

When you underwrite a rental, "income" means the effective rent you built in the Deal Analysis guides. When a lender underwrites you, "income" means something narrower and more standardized — and confusing the two is how borrowers get surprised at application. Here's the method a conventional (Fannie Mae–style) lender actually uses on a subject investment property, and what it means for you.

First — before any math — the eligibility gate. Most explainers jump straight to the formula, but Fannie's rules ask a prior question: may this borrower use the rental income to qualify at all, and how much? For a subject 1–4-unit investment property it depends on borrower facts. If you have a current primary housing payment and documented property-management experience, the rental income can be used with no restriction. If you have a housing payment but no management experience, the rental income can only be used to offset that property's PITIA (it can't add to your income). And if you have no current primary housing payment, no rental income may be used to qualify. So "how much rent counts" starts with which of those buckets you're in — the arithmetic below only matters once you're allowed to do it. (For the canonical illustration, assume the borrower is in the unrestricted bucket — a current housing payment plus management experience.)

Now the rent figure. The lender doesn't take your word for the rent or use your optimistic pro forma. When rental income is used to qualify on a subject investment property, Fannie requires Form 1007 (the "Single-Family Comparable Rent Schedule," one unit) or Form 1025 (two to four units) to support the income potential; and depending on the transaction and rental history, a current lease may also be required or may supply the gross-rent amount, subject to Fannie's support rules. So the starting number is the appraiser's market rent and/or the qualifying lease — not your asking rent.

Then comes the haircut that surprises people. When the qualifying rent is being derived from a lease or Form 1007/1025, the lender multiplies the gross monthly rent by 75%. That's a fixed factor: Fannie treats the missing 25% as absorbed by vacancy and ongoing maintenance. So $2,200 of market rent becomes $1,650 of countable rent. Right there is P16: your revenue is not the lender's income. Note the scope: this 75% method applies when a lease or Form 1007/1025 is the source. If instead the income is being documented from Schedule E (tax-return history), Fannie uses a different method — adding back depreciation, interest, HOA dues, taxes, and insurance to the reported figure. Same goal, different pathway; the 75% haircut isn't universal across every rental-income calculation.

Now the part that decides whether rent helps you qualify — for a non-owner-occupied property like the canonical deal. The lender compares that 75% qualifying rent against the entire mortgage payment — not just principal and interest, the full PITIA: Principal, Interest, Taxes, Insurance, and any Association dues. The result is your net rental income: 75% of gross rent − PITIA. If it's positive, it's added to your income and helps you qualify; if it's negative, it becomes a monthly obligation that counts against you. (Treatment differs for rental income from your principal residence — there the qualifying rent is added to income and not netted against the payment, with the full PITIA kept in obligations. The owner-occupied / house-hack branch has its own guide; don't apply the investment-property netting there.)

Watch it land on the canonical deal — under the illustrative assumption that the borrower may use the rental income without an additional restriction. Market rent is $2,200, so 75% is $1,650. The full PITIA is about $1,651 (principal-and-interest $1,259, plus roughly $283 of property tax and $108 of insurance a month, no HOA). Net rental income: about $0 — so the property's contribution to the borrower's debt-to-income picture is roughly neutral. And here's the P16 kicker: that same property, in your real underwrite, runs a true cash flow of about −$913 a year. The lender's qualification math says "a wash"; your bank account says "a small monthly cost." Both are correct — they're measuring different things. The lender's 75%-minus-PITIA is a standardized qualification test, not a forecast of your cash.

This is why the LTR version of P16 is "closer, not automatic." For a short-term rental, the gap between your revenue and the lender's counted income is enormous — nightly revenue is nothing like a 75%-of-market-rent figure. For a long-term rental, the lender is literally using long-term market rent, so the two numbers live in the same neighborhood. But "closer" isn't "the same": you first have to clear the eligibility gate, the 25% haircut is standardized rather than your actual vacancy, the full PITIA is netted out, and whether it's the lease or the market rent that governs follows the lender's rules. Don't walk in assuming your $2,200 rent is $2,200 of qualifying income — it isn't, and on a thin deal the difference can decide approval.

One boundary to keep clean, because it connects to the DSCR guide. Everything above is the conventional, debt-to-income path — the lender is folding this net rental figure into your personal income-and-debt picture. A DSCR-program loan uses a different, property-coverage qualification framework rather than this conventional Fannie rental-income/DTI method; the exact borrower, income, reserve, and underwriting requirements vary by program and belong in the next guide. Same borrower, same property, two different qualification methods — and the conventional-vs-DSCR choice is its own guide.

So the plain-English version: a conventional lender first checks whether you're even allowed to use the rental income (and whether it's restricted), then — when a lease or Form 1007/1025 is the source — keeps 75% of the rent, subtracts the whole payment (PITIA) on an investment property, and only the leftover counts toward qualifying you. It's closer to your reality on a long-term rental than a short-term one, but it's still a standardized test with an eligibility gate in front of it, not your cash flow — which is exactly why the canonical deal can be "$0 to the lender" and "−$913 to you" at the same time.

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The bottom line

A conventional lender doesn't count your rent — it first checks whether you're allowed to use the rental income at all, then (on the lease/1007/1025 method) counts 75% of the rent minus the entire mortgage payment (PITIA) on an investment property, and only the remainder helps you qualify. For a long-term rental that's closer to your real numbers than it is for a short-term one, but it's still a standardized test with an eligibility gate in front of it, not a cash-flow forecast. The canonical deal makes the gap vivid: about $0 of qualifying income to the lender, and about −$913 a year of real cash to you. Know which number you're looking at.

About the author

Matt Nunn is the founder of Builders Finance. He has spent two decades working with the financial side of real estate businesses, and started Builders Finance to give short-term-rental operators the financial systems, frameworks, and plain-language education that most hosting advice skips over. Builders Finance publishes educational content for STR owners; it is not legal, tax, or investment advice, treatment depends on your facts and circumstances, and it is not a substitute for guidance from your own qualified professionals.

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This resource provides general educational information and is not individualized lending advice. Lender guidelines change and vary by program; verify current requirements (including Fannie Mae B3-3.8-01 and the applicable forms) with your own lender.

Primary sources (verified at draft; re-verify at publish): Fannie Mae Selling Guide B3-3.8-01, Rental Income (current as of Aug. 20, 2026; substantive material dated 10/08/2025 — the section was relocated from the former B3-3.1-08 under the Selling Guide reorganization) — the eligibility/restriction gate for subject 1–4-unit investment property (housing-payment + management-experience conditions), Form 1007 / Form 1025 plus lease support, the 75% (25% vacancy/maintenance) factor for the lease/1007/1025 method vs. the Schedule-E add-back method, net-rental-income = 75% of gross − full PITIA for a non-owner-occupied property (positive-to-income / negative-to-obligation) and the distinct principal-residence treatment. BFC Financing P16 (your revenue is not the lender's income). Canonical PITIA computed from the locked deal assumptions. Fannie conventional guidance is freshness-sensitive; DSCR-program qualification differs (its own node).