Rex says
Money math without the spreadsheet headache. Plug in your numbers and I'll show you exactly where the dollars land.
Try a scenario
Click to load — tweak from there.Inputs
Result
Equity captured at acquisition
$62,000
Monthly cash flow spread
$550
Cash-on-cash return
60%
Annual cash flow
$6,600
Total cash invested
$11,000
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How to use this
- 1Enter property value ($).
- 2Enter existing mortgage balance ($).
- 3Enter existing monthly piti payment ($).
- 4Enter market rent (or your rent if owner-occupying) ($).
- 5Enter cash paid to seller at closing ($).
- 6Enter closing / transfer costs ($).
- 7Read your equity captured at acquisition on the right — it updates as you type.
- 8Hit Share to keep the scenario or send it to someone.
About this calculator
In a subject-to deal, you take title to a property while the existing mortgage stays in the seller's name and you make the payments — no new loan, no qualifying, no due-on-sale trigger event unless the lender chooses to enforce it (a real risk worth understanding, not a footnote). This calculator computes the equity you're effectively acquiring (property value minus the existing loan balance minus any cash you pay the seller), the monthly cash flow spread between market rent and the existing PITI payment, and your cash-on-cash return based only on the cash you put in — which is often just closing costs and any seller payment, not a full down payment. That capital efficiency is the entire appeal of subject-to: you control an asset and its equity for a fraction of the capital a traditional purchase requires. The tradeoff is the due-on-sale clause risk in nearly every conventional mortgage, meaning the lender can technically call the loan due upon transfer of title, even though enforcement in owner-occupant-to-investor subject-to deals is statistically uncommon.
Worked example
Using the values the calculator loads with:
Inputs
- Property value: 280000 $
- Existing mortgage balance: 210000 $
- Existing monthly PITI payment: 1650 $
- Market rent (or your rent if owner-occupying): 2200 $
- Cash paid to seller at closing: 8000 $
- Closing / transfer costs: 3000 $
Results
- Equity captured at acquisition: $62,000
- Monthly cash flow spread: $550
- Cash-on-cash return: 60%
- Annual cash flow: $6,600
- Total cash invested: $11,000
What each field means
Inputs
- Property value ($)
- The property value used in the calculation, measured in $. Starts at 280000 $ so you have a working example on load.
- Existing mortgage balance ($)
- The existing mortgage balance used in the calculation, measured in $. Starts at 210000 $ so you have a working example on load.
- Existing monthly PITI payment ($)
- The existing monthly piti payment used in the calculation, measured in $. Starts at 1650 $ so you have a working example on load.
- Market rent (or your rent if owner-occupying) ($)
- The market rent (or your rent if owner-occupying) used in the calculation, measured in $. Starts at 2200 $ so you have a working example on load.
- Cash paid to seller at closing ($)
- The cash paid to seller at closing used in the calculation, measured in $. Starts at 8000 $ so you have a working example on load.
- Closing / transfer costs ($)
- The closing / transfer costs used in the calculation, measured in $. Starts at 3000 $ so you have a working example on load.
Results
- Equity captured at acquisition
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Monthly cash flow spread
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Cash-on-cash return
- Returned as a percentage. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Annual cash flow
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Total cash invested
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
What is the due-on-sale risk in plain terms?
Nearly every conventional and FHA mortgage has a clause letting the lender demand full repayment if title transfers without their consent. In practice, lenders rarely enforce this on performing loans because it costs them money to call a loan that's being paid on time, but it is a real contractual right, and rate environments where the underlying rate is well below market increase the incentive for a lender or loan servicer to enforce it.
How is this different from a wraparound mortgage?
In a straight subject-to, the buyer pays the existing lender directly (or through a servicing arrangement) and there's no new note between buyer and seller. A wraparound adds a new note from buyer to seller at a rate that's typically higher than the underlying loan, with the seller keeping the spread, which changes the cash flow and risk allocation from what this calculator models.
Why would a seller agree to this?
Common motivations: they're behind on payments and want to avoid foreclosure, they're relocating and can't sell for enough to cover the loan plus costs, or they inherited a property with a mortgage they don't want to keep paying. The seller's credit stays tied to the loan until it's paid off or refinanced, which is a real risk for them if the buyer stops paying.
Should equity captured count as immediate profit?
No — it's paper equity, not cash, and you only realize it by selling or refinancing later. Treat it as a factor in total return alongside cash flow, not as money in hand, and remember you're also taking on the loan payment obligation and property management responsibilities that come with it.
Accuracy and limitations
- Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
- Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.
- This is educational maths, not financial advice. Check anything contractual with the lender or your accountant.
Related tools
Seller Financing Note Yield Calculator
Calculate the effective yield a seller earns carrying a note, including any discount.
Hard Money Bridge Loan Total Cost Calculator
Total all-in cost of a short-term hard money or bridge loan, points included.
BRRRR Refinance Capture Calculator
How much cash you pull out (or leave in) on the refinance step.
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Subject-To Deal Math Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/subject-to-deal-math
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/subject-to-deal-math" target="_blank" rel="noopener">Subject-To Deal Math Calculator — RevenueLab</a> (2026).</p>
Source: [Subject-To Deal Math Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/subject-to-deal-math) (2026).