Underwriting Seller-Financed Deals Without Fooling Yourself

Why Seller Financing Tempts You Into Bad Math

Seller financing feels like a cheat code. No bank underwriting, no appraisal contingency killing your deal, flexible terms you can negotiate face-to-face. That flexibility is exactly why so many investors talk themselves into deals that never would have cleared a lender's desk.

When a bank says no, sometimes it's protecting you from yourself. When you remove the bank, you become the underwriter. Most people are terrible at underwriting their own optimism. So let's talk about how to do it without fooling yourself.

The Rate Is Only Half the Conversation

Investors fixate on the interest rate because it's the number they know how to compare. But a seller-financed note has four levers, and the rate is just one:

• Interest rate — the obvious one
• Amortization period — how the payment is calculated
• Term / balloon — when the whole thing comes due
• Down payment — how much cash you're actually risking

A seller will happily trade you a low rate for a short balloon, or a small down payment for a rate that eats your cash flow. Say a seller offers 5% on a $400,000 note amortized over 30 years — sounds great. Then you notice the balloon is at year 3. You now have 36 months to refinance or sell, and if rates or your credit or the property's performance don't cooperate, you're forced into a fire sale or a default.

Run the actual payment on the calculators before you get emotionally attached to the rate. A 5% rate with a 3-year balloon is a completely different risk profile than 7% fully amortized.

Stress-Test the Balloon First, Not Last

The balloon is where seller-financed deals go to die. Every balloon assumes a future event: you'll refinance into a conventional loan, or you'll sell, or you'll have the cash. Underwrite each of those as if it might fail.

Ask yourself, honestly:

• If I have to refinance at balloon, what LTV and DSCR will a lender require, and does the property support it at higher rates than today?
• If I have to sell, am I confident the property is worth more than the balloon balance, net of selling costs?
• If neither works, can I carry the payment indefinitely and negotiate an extension from a position of strength?

If your only answer to the balloon is "rates will come down" or "values will rise," you don't have a plan — you have a hope. Model the refinance at a payment 2 percentage points above today's rate. If the deal still services debt at that number, you have real margin. If it only works at today's rate, you've built your deal on a forecast.

Underwrite the Cash Flow Like a Skeptic

Seller financing doesn't change the fundamentals of the property. It just changes who holds the paper. Run your income and expenses the same way you would for any acquisition — vacancy, real maintenance reserves, capex, management even if you self-manage. Don't let a friendly seller and a handshake deal tempt you into skipping the boring line items.

A quick illustrative example: a $400,000 property with $36,000 gross rent, minus a realistic 40% for operating costs and reserves, leaves roughly $21,600 in NOI. On a 30-year amortizing note at 7% for $360,000, debt service runs about $28,700 a year. That deal is negative before you've turned on the lights — and no amount of seller flexibility fixes negative NOI-to-debt coverage. Feeding a deal like this from your W-2 is not investing.

Run it through the analyzer with conservative inputs and see whether the numbers survive contact with reality.

Protect Yourself in the Paper

Underwriting isn't only spreadsheets — it's the note and the deed of trust. A few clauses that quietly determine your risk:

• Prepayment penalties — can you refinance early without a fee?
• Due-on-sale interaction — if the seller has an underlying mortgage, a wrap can be called by their lender
• Default cure periods — how much room do you have if a tenant blows up your month
• Substitution or release clauses — flexibility if you want to sell one property in a package

A good rate wrapped in hostile terms is a bad deal. Have a real estate attorney read every line before you sign, not after.

Know the Market You're Buying Into

Your balloon exit depends entirely on the local market's trajectory and lending conditions at maturity. Pull the market reports for the area and ask whether it's the kind of market where a refinance or resale in three years is plausible — or one where you'd be praying for a buyer.

Concrete takeaway: Before you sign, write down the exact number the property must refinance or sell for at balloon, calculated at a rate 2 points above today's. If you can't say that number out loud with confidence, you're not ready to buy the deal — you're ready to negotiate a longer term.