How to Calculate Seller Financing Payments

Seller financing gets confusing when the purchase price, the monthly payment, and the balloon are discussed as if they mean the same thing. They do not.

The monthly payment comes from the amount the seller is financing, the interest rate, and the amortization period. The balloon says when the remaining unpaid balance becomes due.

If you already know the terms and only want the answer, use the free seller financing calculator. If you want to understand the math underneath it, start here.

The four numbers you need first

1. Purchase price — the agreed price for the property.
2. Down payment — cash paid at closing.
3. Interest rate — the annual rate on the seller-financed balance.
4. Amortization period — the schedule used to calculate the payment.

The financed principal is:

Financed principal = Purchase price − Down payment

On a $500,000 purchase with $50,000 down, the seller is financing $450,000.

The monthly payment formula

For a fully amortizing fixed-rate note:

Payment = P × r(1+r)^n ÷ ((1+r)^n − 1)

Where P is financed principal, r is the monthly interest rate, and n is the total number of monthly payments in the amortization schedule.

At 5% annual interest, the monthly rate is 0.05 ÷ 12. A 30-year amortization has 360 monthly periods.

Using $450,000 financed at 5% over 30 years produces a payment of about $2,416 per month in principal and interest.

What a balloon changes

A balloon usually does not change that scheduled payment. It changes when the remaining balance becomes due.

For a $450,000 note at 5%, amortized over 30 years with a 5-year balloon, the borrower makes 60 scheduled payments and then owes the remaining principal.

That remaining balance is approximately $413,229.

So “30-year amortization with a 5-year balloon” means the payment is calculated as though the loan ran for 30 years, but the unpaid balance matures after five.

For a full walkthrough, see the 30-year amortization with a 5-year balloon example.

How to calculate the balloon balance

The remaining balance after a certain number of payments can be estimated with:

Balance = P(1+r)^k − Payment × ((1+r)^k − 1) ÷ r

k is the number of payments made before the balloon. For a five-year balloon with monthly payments, k = 60.

Real payoff statements can differ slightly because of payment timing, accrued interest, servicing conventions, fees, or other note terms, but this is the core amortization math.

Reverse seller financing: start with the payment

Sometimes a seller does not begin with a rate or purchase structure. They begin with an outcome:

“I need $2,000 a month.”

In that case, solve for the principal the payment can support:

Principal = Payment × (1 − (1+r)^−n) ÷ r

At 5% interest and 30-year amortization, a $2,000 monthly payment supports about $372,563 of seller-financed principal. Add $50,000 down and the corresponding purchase price is roughly $422,563.

That does not establish market value. It tells you which purchase price is mathematically consistent with those financing constraints.

See the full $2,000-per-month reverse financing example.

Do not confuse note payment with property cash flow

A payment can be mathematically correct and still be too expensive for the property. Property income, operating expenses, vacancy, repairs, taxes, insurance, and debt service need to be tested separately.

That is why the calculator keeps the note structure and property analysis in the same workspace. You can solve the financing, then test NOI, cash flow after debt, DSCR, and cash-on-cash return without rebuilding the deal.

A quick checklist before relying on the answer

• Purchase price and cash down
• Seller-financed principal
• Fixed or variable interest rate
• Amortization period
• Balloon or maturity date
• Any interest-only period
• First-payment timing
• Whether taxes, insurance, servicing, or other fees are separate

A calculator solves the math. The actual signed documents determine the obligation.