An assumable mortgage lets a qualified buyer take over the seller's existing loan on its original terms, low rate included, and in a normal sale that means government loans: FHA, VA, and USDA. Conventional fixed-rate loans, plus essentially every portfolio loan from banks, non-QM lenders, or funds, carry a due-on-sale clause that lets the lender call the balance due when the home is sold, and they enforce it. One carve-out worth knowing: federal law protects certain transfers, like divorce, death, or a transfer to a spouse or child, where the remaining party can assume and continue a conventional loan at its existing rate. That helps families in transition, and it does nothing for a buyer in an arms-length sale. Many adjustable-rate mortgages are also assumable. When a loan is assumable, you apply directly with the seller's current servicer and qualify under that program's standard guidelines, so approval is never automatic. Expect it to be slow. Servicers are not set up for assumptions, are not especially motivated, and can only charge a limited processing fee, so the work is no moneymaker for them. The biggest practical wall is equity. If the home was bought at a low balance and has appreciated substantially, you have to cover the gap between that old loan and today's price. Say the seller now has six figures of equity: you either bring that in cash or layer a second mortgage on top at current market rates. That second blends with the low first, and the effective combined rate can climb toward ordinary market territory, erasing much of the appeal. Where we have seen assumptions actually close, it is usually VA-to-VA with a buyer holding real cash from a prior sale. Worth exploring on FHA and VA listings; go in expecting a slog and a cash gap.