Interest-Only Payment Math for Investors

Interest-Only Payment Math for Investors | Kings of Capital

Short-term investor loans often use interest-only payments. The idea is simple, but the math trips people up when they budget a flip or fix and flip loans a bridge. This guide walks through the formula and shows why the balance stays flat during the interest-only period.

Every number below is a made-up illustration. None of it is a market rate, a lender rate or a quote.

What interest-only means

During an interest-only period, your payment covers the interest that accrues and nothing else. You do not pay down principal. The balance at the start of the period is the balance at the end, unless you make extra payments.

That keeps the monthly payment lower than a fully amortizing payment on the same balance. The cost of that benefit is that you still owe the entire amount when the period ends.

The basic formula

Take the loan balance, multiply by the annual interest rate, and divide by 12. That gives a monthly interest-only payment. If the balance changes, as it does on rehab loans with draws, the figure changes too.

A hypothetical walk-through

Assume a plainly hypothetical annual rate of 10%, used for illustration only. Assume a $200,000 balance.

Annual interest: $200,000 times 0.10 equals $20,000
Monthly interest-only payment: $20,000 divided by 12, about $1,667
Over a 9-month hold: about $15,000 in total interest

At the end of nine months, the balance is still $200,000. The sale or refinance has to pay it off.

Why draws change the picture

On a rehab loan, funds for repairs are released in stages. You pay interest only on money already sent, not on the full commitment. Suppose half of the funds go out in month one and the rest arrive in month four. The payment starts lower, then steps up. A budget that uses the full balance from day one may overstate early cost. A budget that ignores later draws understates it. Build both months and balances into your sheet. For an independent explanation, see title insurance.

Where interest-only terms appear

The program pages list different interest-only windows. These are offered only to qualified borrowers and subject to change.

Hard money: 3 to 9 months, shown on hard money loans with 3 to 9 months interest-only
Fix and flip: 9 to 18 months, shown on fix and flip loans with 9 to 18 months interest-only
Multifamily bridge: 12 to 36 months, shown on multifamily bridge loans with 12 to 36 months interest-only

Rental loans work differently. The program page lists a 30-year fixed or an ARM structure, so payments there follow amortization. See rental loans that move from interest-only thinking to amortization for that side of the story.

Interest-only versus amortizing

An amortizing payment includes interest and a slice of principal. Early in the term, most of the payment is interest. Over time the principal share grows. By the end, the balance reaches zero.

Here is a rough comparison, still hypothetical. Assume a monthly amortizing payment of $1,755 on the same $200,000 balance. That figure is an assumed payment for illustration only. The interest-only payment of about $1,667 is a bit lower. The gap is small at these assumptions. The difference is that the amortizing loan builds equity by reducing principal each month, while the interest-only loan does not.

Which one fits depends on your plan. A flip that sells in eight months has little reason to pay down principal. A long-term rental often benefits from amortization.

A second hypothetical on a longer hold

Keep the same assumed 10% illustration rate, and now assume a $500,000 balance on a larger project held for 18 months. Annual interest is $50,000. The monthly interest-only payment is about $4,167. Over 18 months, that comes to about $75,000 in total interest, with the full $500,000 still owed at the end. Now imagine the project runs three months long. Three more payments add about $12,500. A delay that looks small on a calendar can be large in dollars.

The same lesson applies at any size. Time is a cost. Every month you hold an interest-only balance adds a payment, so a realistic schedule is part of the math.

Budget the whole hold period

Interest is only one carrying cost. Add taxes, insurance, utilities and any other recurring cost. Then add a buffer in case the project runs late. A delayed sale means extra months of payments, and those months add up.

Try several timelines, not one. Many investors test a base case and a late case. If the late case still works, the plan has margin. You can model the cases with the calculators for estimating interest-only payments on a hypothetical balance, and then replace the sample numbers with your own.

Plan the exit before the period ends

Interest-only periods end on a date, and that date is fixed in your loan terms. Write it down next to your sale or refinance target. If the two dates are close, there is little room for delay. Many investors aim to finish the exit a month or two before the period ends, so a late appraisal or a title question does not cause a scramble. Because the balance does not shrink, the exit carries the weight. Know whether you will sell, refinance, or pay from other funds. If you plan to refinance into a long-term loan, line up that step early. Appraisals, title and conditions take time.

Next steps

The 60-second survey on the homepage asks about your property, purpose and timeline. It needs no documents, fees or hard credit pull, and the lender states that preliminary terms come back within one business day. Read about Kings of Capital programs that offer interest-only periods to see which products might match.

If you want to compare payment scenarios with a person, book a call to compare interest-only payment scenarios. For written questions, contact the lender about interest-only terms for your deal.

This is general education, not tax, legal or investment advice. Consult your CPA or attorney about interest treatment. Rates are priced to the deal, and approval is never guaranteed.