The fourplex deal lab

Does the deal work—or just look good?

Screen an existing property or a ground-up build with the same yardstick. Change any assumption and see the decision move immediately.

Editable example: round numbers are loaded to show how the tool works. Replace every field.

Open calculator

Your assumptions

Put each option on the same page

Cost stack

Purchase price ($)

Immediate repairs / reserves ($)

Closing and professional costs ($)

Income + financing

Average rent per unit / month ($)

Income-producing units

Vacancy allowance (%)

Operating expense allowance (%)

Cash / equity in (%)

Interest rate (%)

Amortization (years)

First read

-$1,026/ year after debt

Needs work

The model does not currently cover its debt service.

All-in cost: $1,163,000
Cash required: $290,750
NOI / year: $61,697
Cap rate: 5.30%
DSCR: 0.98
Break-even rent: $2,084 / unit
Debt / month: $5,227
Cash-on-cash: -0.35%
Price / door: $290,750

Cost stack

Land acquisition ($)

Hard construction cost ($)

Design, permits and soft costs ($)

Carry and contingency ($)

Income + financing

Average rent per unit / month ($)

Income-producing units

Vacancy allowance (%)

Operating expense allowance (%)

Cash / equity in (%)

Interest rate (%)

Amortization (years)

First read

-$7,618/ year after debt

Needs work

The model does not currently cover its debt service.

All-in cost: $1,695,000
Cash required: $508,500
NOI / year: $77,702
Cap rate: 4.58%
DSCR: 0.91
Break-even rent: $2,635 / unit
Debt / month: $7,110
Cash-on-cash: -1.50%
Price / door: $423,750

Read the result

A five-minute screen, not a green light

Stress the income

Lower rent, add vacancy and raise expenses. If the deal only works at the best case, it does not yet work.

Interrogate the cost

For an existing building, price condition. For a build, price delays, carry and contingency—not only construction.

Take it to evidence

Replace the screen with leases, utility bills, tax records, insurance terms, lender quotes and physical inspection.

Open the property checklist

What this calculator does: transparent arithmetic on the assumptions you enter. It is not a valuation, appraisal, lending decision or forecast. Confirm financing, tax, legal and construction assumptions with qualified professionals.