Analyze the full cash-flow stack before you offer

A rental offer can go wrong quietly. You walk the house, you like the street, you hear a rent number that feels fair, and you write a price that still seems to work if that rent is real and vacancy stays short.

Then the first year shows what the worksheet left out.

This lesson is the cash-flow stack: every dollar that has to come out of rent before you call the deal cash-flow positive.

The maximum offer is what remains after that stack — not the price you hope the seller will accept.

We will use one example property. The numbers are assumptions for the worksheet, not a market study of any real listing.^[1]

Start with income you can defend

Gross rent is not the same as take-home income.

It is what comparable occupied rentals are actually collecting, adjusted for condition and unit mix. If three similar three-beds within a mile are leasing at $1,650 to $1,750, you cannot treat a $1,900 ask on a tired kitchen as the rent you will collect.

Write the rent as a range: use the middle for the base case and the low end for the stress case.

The same discipline that keeps a flip ARV honest applies here: recent leases, same product type, same school or amenity draw, and a clear note when you are stretching.^[2]

For a longer look at comps as an offer screen, see the flip-track post on finding and analyzing deals — the habit transfers even though the exit does not.

On our teaching house at 1847 Birch Lane, we will use $1,700/month as the base rent and $1,600 as the stress rent. Annual gross at base: $20,400.

Put vacancy on the budget as its own line

Even a “good” rental is empty sometimes. Turnover, make-ready, and the week the lease starts all reduce rent collected. Many underwriters use 5 to 8 percent of gross as a starting vacancy allowance for a single long-term rental; some markets need more.^[3]

On Birch Lane we will use 7 percent of gross for the base case: about $1,428 a year, or roughly one month of rent. That is not a prediction of your next tenant. It is a budget so you do not spend the empty month twice — once when the unit is empty and again if you had not budgeted for it.

Effective gross income at base: $20,400 − $1,428 = $18,972.

The operating stack under the rent

After effective gross, list the operating costs that continue every year — taxes, insurance, management, maintenance, and CapEx reserves.

Net operating income (NOI) before debt: $18,972 − $9,138 = $9,834.

Two notes that matter.

1. First, price management even if you plan to self-manage. Your time is not free, and a future you may hire help.

2. Second, CapEx reserve is not the same as the toilet repair line. The reserve is for the systems that fail on a multi-year clock. Without that reserve, early years look better on paper, and later repairs hit the checking account with no savings set aside.

If you keep a living budget of repairs and reserves on a held asset, budget tracking is a useful place to keep those categories so they do not get lost under miscellaneous expenses.

Debt service comes after NOI, not beside it

Suppose you finance $195,000 at 6.75 percent for 30 years. Principal and interest is about $1,265/month, or $15,180/year.^[4]

Cash flow before income tax: $9,834 − $15,180 = −$5,346.

Here is the point: at $1,700 rent and a full stack, this purchase price does not produce positive cash flow.

The house can still be a fine long-term hold if appreciation, principal paydown, and your tax picture support it — but you should not call it cash-flow positive while the sheet says otherwise.

Work backward. If you need break-even cash flow with this operating stack and this loan rate, annual debt service cannot exceed NOI. At $9,834 of NOI, maximum annual P&I is $9,834, or about $820/month. On a 30-year loan at 6.75 percent, that supports roughly $126,000 of loan.

With 25 percent down, the max purchase is near $168,000 — not the $260,000 ask that looked close when you only compared rent to the mortgage payment.

A short max-offer checklist

Rent from comps — use a low and mid range from comparable leases, not the asking rent on the flyer.

Vacancy allowance — put it in dollars on the sheet, even if you expect a quick lease-up.

Taxes and landlord insurance — from real quotes or last year’s bills, plus a small buffer.

Management — include a market percent even if you plan to self-manage.

Maintenance and CapEx — keep them as separate lines.

Debt service — use the loan you will actually close, including taxes and insurance in escrow if the lender requires it.

Max offer — set it from the income that remains after the full stack, then decide whether you will still bid for other reasons.

It is normal to like a house. Still, set the offer from the numbers, not from how you feel about the tour.

Running the full stack keeps a house you like from becoming an offer the numbers do not support.

If two scenarios disagree, a side-by-side in comparison tools can hold the base case and the stress rent without rewriting the sheet by hand.

Deal-killer thresholds belong here too: if vacancy, insurance, or tax reassessment would push cash flow through zero, you want that visible before your earnest money is hard to get back — not after the first empty month. See deal-killer alerts when you want those limits on a live underwrite.

What this lesson is not

This is not a claim that every rental must cash-flow on day one. Some investors buy thin cash flow for basis, location, or a planned rent step-up. The requirement is honesty: name the subsidy you are willing to pay, and size the offer from the stack, not from a finish or room you liked on the tour.

The next lesson prices the vacant stretch itself — make-ready delay and empty days — so “cash-flow positive” does not mean “positive the week after closing.”

Write the cost stack before you write the offer. Gross rent is the starting line on the sheet, not the amount you can afford to spend. The offer should be the purchase price that still works after the full stack.

If you want to underwrite the full cash-flow stack on an address you are looking at, start a 30-day trial.

Next up: Negative cash flow until it’s occupied — how to price the risk — price the vacant stretch before you call it cash-flow positive.