How assumable mortgages work, with an example

What an assumable mortgage is

An assumable mortgage lets a qualified buyer take over the seller's existing loan—balance, rate, and remaining term—after the lender or servicer approves the transfer. The buyer becomes the borrower. That is the opposite of a subject-to purchase, where the deed moves but the loan stays in the seller's name without lender approval.

FHA, VA, and USDA loans are the programs most often discussed as assumable, each with its own credit, fee, occupancy, and liability rules. Most conventional fixed-rate loans are not assumable in a normal sale because of due-on-sale clauses that the Garn-St Germain Act (12 U.S.C. 1701j-3) generally lets lenders enforce.

The appeal is the rate: if the seller locked in 3% when market rates are near 7%, the monthly principal and interest can be hundreds of dollars lower. The catch is the equity gap, the approval process, and program fees that do not disappear just because the rate is low.

How the money moves

At closing, the purchase price splits into the assumed balance and everything else. The equity gap—price minus balance—is paid in cash, with permitted secondary financing, or a mix. On top of that sit the assumption fee the servicer quotes, buyer closing costs, and any extra cash for repairs or prepaid items, minus seller credits.

After closing, you make the assumed payment and any second-loan payment, plus taxes, insurance, and operating costs. If you rent the house, cash flow is rent after vacancy minus that full stack. Cash-on-cash divides yearly cash flow by the cash you brought to close.

Always compare two new-loan paths: (1) a new loan on the same balance at today's rate, which isolates the rate edge on the note, and (2) a new purchase loan sized so your cash into the deal matches the assumption's cash to close, which compares the whole structure.

Formula

Equity gap = purchase price − assumed loan balance. Cash need before gap = equity gap + assumption fee + closing costs − seller credits + extra cash. Cash to close = cash need − gap loan amount.

Assumed P&I is the typed payment, or the amortizing payment on the balance, rate, and years left. PITI = assumed P&I + monthly tax + monthly insurance. Monthly cash flow = rent × (1 − vacancy) − PITI − gap payment − other monthly costs. Cash-on-cash = yearly cash flow ÷ cash to close.

Rate edge = new-loan P&I on the same balance at today's rate and term − assumed P&I. Full-deal edge = new purchase P&I (price − cash to close) − (assumed P&I + gap payment). Blended rate = weighted average of the assumed rate and gap rate by balances. Exit profit = sale value − selling costs − remaining assumed and gap balances + hold cash flow − cash to close.

Example

Illustrative example. These are the same sample numbers the assumable mortgage calculator opens with. They are not a real property, seller, loan, or approval. A house is worth $400,000 and sells for $400,000. The seller's assumable loan balance is $280,000 at 3.5% with 27 years left. The assumption fee is typed as $1,400, buyer closing costs are $6,000, and the seller credits $2,000. There is no gap loan in the base case.

Cash to close: the equity gap is $120,000. Add the $1,400 fee and $6,000 of closing costs, subtract the $2,000 credit, and cash to close is $125,400. Day-one equity is $120,000 (value − assumed balance).

Monthly: the assumed principal and interest is $1,337.08. Add $350 of property tax and $150 of insurance and the PITI is $1,837.08. Rent of $2,800 with 5% vacancy brings in $2,660. After the PITI and $200 of other costs, the house cash flows $622.92 a month, or $7,475.04 a year. Divided by the $125,400 to close, that is a 6.0% cash-on-cash return.

The rate edge: the same $280,000 borrowed new at 7% over 30 years (a sample rate; check today's quotes and type yours) would cost $1,862.85 a month, $525.77 more than the assumed loan. Lifetime interest on the remaining assumed schedule is about $153,212 versus about $390,622 on that same-balance new loan, a rough savings of $237,410—different terms, so treat it as an edge, not a promise. A new purchase loan with the same $125,400 cash in would be $274,600 at 7% / 30 years, or $1,826.92 a month—$489.84 more than the assumed P&I alone.

The exit: hold 5 years at 3% a year and the house is worth about $463,710. Selling costs of 6% are $27,823, and the assumed loan is down to $245,931, so the sale nets $189,956. Add $37,375 of cash flow over the 5 years and subtract the $125,400 you put in, and the profit is $101,932 before income tax. A rough annual IRR on those yearly cash flows is about 13.8%.

Optional gap financing: if instead you borrowed $50,000 of the equity gap at 8% over 15 years, the gap payment would be about $477.83, cash to close would fall to $75,400, and the blended rate on $330,000 of total debt would be about 4.18%. That path only works if the first loan's servicer allows the second lien.

Assumption vs subject-to

In a formal assumption the servicer approves you, you become the borrower, and—when the program allows—the seller can seek a written release of liability. In a subject-to deal the deed moves without that approval, the loan stays in the seller's name, and the due-on-sale clause still applies. Use the subject-to calculator when you are modeling that path, and this calculator when you are modeling an approved assumption.

Neither path is a shortcut around honesty with the lender, title company, and insurer. If you need seller financing layered on top of an assumption, or a wrap, federal loan-originator rules and state licensing can also apply—ask a real estate attorney in the property's state.

Common pitfalls

Underwriting the rate alone and ignoring the equity gap. A 3% loan on a house that needs $120,000 cash at closing is a different deal than the payment suggests.

Assuming secondary financing is allowed. Many first-lien programs limit or ban a second mortgage used to cover the gap. Confirm before you count on it.

Treating a listing that says "assumable" as approval. Only the servicer's written process and closing documents create an assumption.

Skipping release of liability and, on VA loans, entitlement questions. Those are separate from "the buyer can make the payment."

Comparing lifetime interest across unequal terms without saying so. A 27-year remaining schedule and a fresh 30-year loan are not identical clocks.

Sources

Due-on-sale enforcement and its exceptions: Garn-St Germain Depository Institutions Act, 12 U.S.C. 1701j-3. Program assumption rules are set by the Federal Housing Administration (HUD), the Department of Veterans Affairs, and USDA Rural Development, and by each loan's servicer—confirm current fees, credit standards, and release-of-liability steps with the servicer on the loan you are underwriting. This page does not quote fee schedules that change.

Steps

1. Confirm the loan is assumable

   Ask the loan servicer in writing whether the note allows assumption and what credit, occupancy, and fee rules apply. Do not rely only on listing language.

2. Measure the equity gap

   Subtract the remaining loan balance from the purchase price. That gap is cash or permitted secondary financing you must cover, plus assumption and closing costs, minus any seller credits.

3. Apply and qualify with the servicer

   Submit the assumption application with income, credit, assets, and program paperwork. Approval puts you on the note; it is not the same as a subject-to purchase that leaves the seller as borrower.

4. Compare assumed payments with a new loan

   Run the assumed principal and interest against a new loan on the same balance at today's rate, and against a new purchase loan with the same cash into the deal, so you see the monthly and lifetime interest edge.

5. Close with release of liability where available

   Coordinate title, assumption documents, fees, any secondary financing the first loan allows, and—when the program permits—the seller's written release of liability. For VA loans, ask separately about entitlement restoration.

Questions