A mortgage-only surplus can look much larger than the money actually left for the owner.
A tempting number that leaves bills unpaid
At $3,200 rent and $1,264.14 principal and interest, a mortgage-only subtraction suggests $1,935.86 a month. This is the same hypothetical $400,000, 50%-down example used in our cash-flow guide—not a property listing or achievable-rent estimate.
The debt payment does not include tax and insurance escrow here. Listing them separately avoids double-counting. The apparent surplus still has to cover vacancy, operating costs and long-term replacements.
Follow every deduction
This example assumes 5% vacancy/collection loss; 8% management of collected rent; separate 5% repairs and capital allowances; and a 0.75-month leasing fee every 24 months. Annual property tax is 1.2% of price. HOA is $100, insurance $125, utilities $50 and administration $25 monthly. Other owner costs are an explicit zero assumption.
| Step | Monthly amount |
|---|---|
| Scheduled rent | $3,200.00 |
| Less vacancy/collection allowance | $160.00 |
| Less operating costs | $1,203.20 |
| Less principal & interest | $1,264.14 |
| Less capital reserve | $160.00 |
| Cash left before income tax | $412.66 |
A reserve is not an evenly timed repair bill
The capital reserve smooths expected replacements for a stabilized planning month. A roof replacement may be much larger than one month’s allowance and may arrive early. Initial make-ready costs and cash kept available after closing remain separate.
For a specific year, model the timing of known work and reserve withdrawals rather than subtracting both the full replacement and its identical reserve allowance. Repairs, turnover work and major capital items should be defined consistently so one cost is neither omitted nor counted twice.
Cash flow is also different from taxable income
The full principal-and-interest payment reduces cash flow, but principal repayment is not a current rental expense deduction. Money merely transferred to a reserve is not automatically deductible. Depreciation is noncash, and loss rules can delay a tax benefit.
This example is before income tax. Do not add an assumed refund or personal deduction benefit to it. Use the tax year and circumstances that actually apply to you when seeking qualified tax advice.
Replace an assumption before polishing the decimal places
Use dated comparable rent evidence, a property-specific insurance quote, post-purchase taxes, HOA documents and actual financing terms. An unknown cost is a research item, not zero. The precision of a payment calculation cannot make an unverified rent reliable.
Try changing a single cost in the linked calculator. Then test several unfavorable inputs together. Your result will show the consequence of those assumptions, not a promise that the property will earn it.
Can I call rent minus mortgage my monthly profit?
It is an incomplete subtotal. Deduct vacancy, operations, tenant-turnover costs and capital reserves, then distinguish before-tax planning from actual cash timing and income taxes.
Sources & review notes
The workflow and hypothetical examples are original RentQuarry educational material. These primary references support the relevant financing or tax distinctions; they do not validate a listing, rent or expense allowance.
- CFPB: Understanding a Loan Estimate
Principal and interest, escrow, closing costs and loan terms. Confirm which disclosures apply to your financing.
- IRS Publication 527: Residential Rental Property
Federal rental expenses, depreciation and loss limitations. Check the tax year that applies to you.
Sources checked November 11, 2026. Worked financing examples are checked against deterministic code and independent arithmetic. This is an editorial and arithmetic review, not an independent professional review. Read our method. Corrections: contact RentQuarry.
What do your numbers say?
Try a hypothetical example without an account. Replace the assumptions with researched inputs and review the limitations before relying on a result.
Try this worked example