Interest-only underwriting and the amortizing refinance test

Interest-only payments can make a property look comfortably covered while leaving a refinancing shortfall at maturity. The initial loan and its replacement may use different rates, amortization, cash-flow definitions, and leverage limits. The relevant exit question is how much net replacement financing can repay the actual maturity balance, not whether the property can make today’s interest payment.

Microsoft’s PMT documentation supports the constant-rate amortizing calculation used below. The example is a financing stress worksheet, not a prediction of future rates or a statement that a lender will refinance the loan. It assumes monthly, month-end replacement-loan payments and carries unrounded results until final display.

Start with the actual maturity obligation

Record the original balance, subsequent advances, capitalized interest, scheduled principal payments, curtailments, and any additional payoff charges. An interest-only loan with no principal changes leaves its original balance outstanding. A loan with future draws or capitalized charges may leave more.

Identify the contractual maturity date and any extension conditions separately. An extension option that requires a fee, coverage test, replacement cap, or lender acceptance is not an unconditional source of extra time. Build the base exit by maturity and show an extension scenario only with its conditions visible.

Keep periodic interest expense separate from principal payoff. A DSCR above one addresses recurring debt service under the chosen definition; it does not mean annual operations can repay the entire loan at maturity.

Compare the initial and replacement payments

Assume a fictional $5 million loan bears 6% interest only and the property generates $420,000 of annual recognized cash flow. There are no principal reductions or additional advances. Annual interest is $300,000, so current coverage is 1.40 times. The maturity balance remains $5 million.

For the exit scenario, assume a 7.5% replacement rate, 30-year amortization, and a 1.25-times coverage requirement. The annual payment constant is approximately 8.390574%. The recognized cash flow permits $336,000 of annual debt service and supports approximately $4,004,494 of gross replacement principal.

The existing payment is affordable under the modeled annual cash flow, yet the exit requires substantial additional capital. The 2% cost is an illustrative proportional deduction, not a statement that real refinancing costs always scale this way.

Verify that another constraint does not reduce the exit further

Assume, separately, that the same $420,000 is also the income used in a simplified direct-capitalization scenario at 6.5%, and that replacement leverage cannot exceed 65% of that value. Value is approximately $6.462 million, and the value-based loan limit is $4.2 million. The cash-flow limit of about $4.004 million is lower in this case.

This calculation is a sensitivity illustration, not an appraisal. A different accepted income, cap rate, leverage limit, or property condition could make value the controlling constraint. Apply each test to the same forecast date and identify which result governs before calculating net payoff proceeds.

If the lender’s minimum loan size or another eligibility condition prevents execution, a positive arithmetic result does not establish financing availability. Preserve that qualitative condition alongside the numerical limits.

Reverse-solve the operating target

To net $5 million after a 2% deduction, gross replacement debt must be approximately $5,102,041. At the assumed 7.5%/30-year payment and 1.25-times coverage, the required recognized cash flow is approximately $535,113. That is $115,113 above the starting $420,000.

The reverse target is useful because it asks whether the business plan has a documented path to the required income before maturity. Identify the leases, collections, expense changes, and completion milestones needed to reach it. Do not call projected rent “recognized cash flow” before the proposed lender accepts the supporting evidence.

Re-run the value limit at that target as well. Solving the coverage equation alone does not waive the other conditions. If additional costs or a required reserve increase net funding deductions, the target rises.

Turn the gap into dated choices

The owner can evaluate additional equity, a principal curtailment, supported operating improvement, a different financing structure, a sale, or a documented extension. Each has a lead time and evidence requirement. An equity commitment subject to future investor approval is not the same as cash already available.

Set a checkpoint sufficiently before maturity to compare actual performance with the required target and to preserve time for alternatives. Record the latest date for ordering reports, obtaining lender feedback, committing additional capital, or beginning a sale process. The worksheet should trigger action when the plan falls behind, not merely report a shortfall at the final payment date.

The completed analysis contains today’s payment coverage, the maturity balance, replacement constraints, net proceeds, and an operating or equity target. That makes the benefit of interest-only payments visible without allowing near-term cash relief to conceal the separate obligation to repay principal.