The equity gap is the single biggest hurdle in most assumable-mortgage purchases. Here's how to calculate it and the common ways buyers cover it.
When a buyer assumes a mortgage, the loan balance almost always covers only part of the purchase price — the rest represents the seller's built-up equity. That difference is the equity gap, and the buyer has to cover it separately from the assumed loan. It is not necessarily the buyer's complete cash-to-close requirement, since closing costs, fees, and any secondary financing costs add on top of it.
Equity gap = purchase price − remaining assumable loan balance
If the buyer doesn't have the full gap in cash, a second mortgage can cover the rest:
Some buyers cover part of the equity gap with gift funds from family. Whether gift funds are allowed, and what documentation is required, depends on the specific loan program and servicer — confirm the rules before counting on gift funds as part of your closing plan.
In some deals, the seller agrees to finance part of the equity gap directly, instead of the buyer using a third-party second mortgage. Terms — rate, repayment period, and whether the first loan's terms even permit this — are negotiated between buyer and seller and should be documented with a real estate attorney.
Second mortgages and other gap financing often carry higher rates than the assumed first mortgage. If the secondary financing is expensive enough, it can significantly reduce, or even eliminate, the savings from assuming a below-market first-mortgage rate. Always compare the blended rate of the combined financing against a new mortgage's rate before deciding.
The blended rate is the balance-weighted average interest rate across the assumed first mortgage and any second mortgage. It gives a single number to compare against a new mortgage's rate, which is more useful than comparing the first mortgage's rate alone once secondary financing is involved. The assumable mortgage calculator computes this automatically from your numbers.
| Category | All cash | Second mortgage | Seller financing |
|---|---|---|---|
| Upfront cash required | Full equity gap | Only the down payment on the second loan | Negotiable |
| Adds a second monthly payment? | No | Yes | Yes, if not paid in full |
| Typical rate | N/A | Often higher than first-mortgage rates | Negotiated with seller |
| Approval required? | No | Yes, from the second lender | Depends on the first loan’s terms |
AssumeList helps buyers search for homes with FHA, VA, and USDA assumable mortgages. Review the property details carefully and confirm all loan information with the seller's mortgage servicer.
Affiliate disclosure: CheapRateMortgage.com may earn a commission if you purchase an AssumeList subscription through links on this page.
Published 2026-07-13. Last reviewed 2026-07-13 by the CheapRateMortgage.com editorial team, an editorial product of United Internet Ventures. This page is general information, not financial advice; consult a licensed professional for your specific situation. See our disclaimer.