07Investor metrics
Cap rate
Net operating income as a percentage of purchase price. The closest thing to a market-comparable yield.
A Rusty Roof Media research tool
Twenty-three ways to underwrite a deal.One report. One defensible answer.
Do The Numbers Work runs any single-family or small multifamily property through the same methodologies an institutional acquisitions desk uses to clear a deal. You input the property and financing. We return cap rate, cash-on-cash, DSCR, IRR, four stress scenarios, and a composite grade in a single PDF you can hand to a lender, a partner, or your future self.
$30 per analysis. No subscription. No upsell. Bundle pricing for active investors.
23
Underwriting methodologies executed per analysis
From the 1% rule to a five-year IRR solved by Newton-Raphson.
< 5 min
From listing URL to delivered report
Smart defaults pre-fill expense ratios you can override.
4
Stress scenarios run on every deal
Vacancy, rate, rent decline, CapEx catastrophe.
$30
Per analysis. Bundle pricing for portfolios.
No subscription. No data resold. No upsell wall.
The problem
Most rental calculators answer the wrong question.
They tell you cash flow at one set of optimistic assumptions. They don't tell you what happens when the basement floods, the tenant breaks the lease, or the Fed moves another seventy-five basis points.
Single-number outputs
A positive cash flow figure at 8% vacancy and 5% maintenance is not an answer. It is a starting point. Without a stress test, it is a guess dressed up as a number.
No methodology disclosed
Free calculators rarely state what is in the formula. We publish ours. You can read every assumption, every weighting, every default before you trust the output.
No comparison set
A 7% cash-on-cash return looks great until you remember a six-month Treasury yields nearly the same with no roof, no tenant, and no capital risk. We benchmark every deal explicitly.
Built for clicks, not capital
Most online calculators exist to capture a lead, sell a course, or point you at a referral mortgage broker. We sell one thing: the report.
Methodology
The math an institutional acquisitions desk uses.
Twenty-three methodologies organized into five categories, every formula and assumption disclosed. A representative sample below.
08Investor metrics
Cash-on-cash return
Annual pre-tax cash flow divided by the cash actually invested. The investor-equity yield.
10Investor metrics
DSCR
NOI divided by annual debt service. The metric most lenders underwrite to. Below 1.20 typically fails.
12Investor metrics
Five-year IRR
Internal rate of return over a five-year hold, including a modeled sale at exit. Solved iteratively via Newton-Raphson.
18Stress testing
Vacancy stress test
Re-runs the model at 10%, 15%, 20%, and 25% vacancy to find the point at which cash flow goes negative.
22Comparative
Opportunity cost comparison
Benchmarks the deal against equivalent capital deployed into the S&P 500, a high-yield savings account, ten-year Treasuries, and a public REIT index.
Five lenses
No single number tells you whether a deal works.
We run the property through five distinct categories of analysis and reconcile the results into one composite grade.
01
Rules of thumb
Fast filters experienced investors use to triage listings before opening a spreadsheet.
02
Investor metrics
The seven calculations institutional underwriters depend on, including the one your lender cares about most.
03
Strategy
Different exits demand different math. We model BRRRR, flip, house hack, and short-term rental projections discretely.
04
Stress testing
Most calculators show one happy-path number. We re-run the deal under vacancy, rate, rent, and CapEx shocks.
05
Comparative
Every deal competes with the S&P, Treasuries, and REITs. We benchmark explicitly so you see the hurdle rate.
How it works
From listing to report in under five minutes.
- Step 01
Enter the property
Address, purchase price, units, rents, taxes, and insurance. We pre-fill industry-standard expense ratios you can override.
- Step 02
Choose a strategy
Long-term rental, BRRRR, flip, house hack, or short-term rental. Each strategy unlocks the strategy-specific math.
- Step 03
Receive the report
A delivered PDF with all twenty-three methodologies, four stress scenarios, the composite grade, and the underlying assumptions.
Pricing
Pay for the report. Nothing else.
Do The Numbers Work is a tool, not a subscription, not a course, not a lead-generation funnel. You pay per analysis.
Single
$30
per report
- One full deal analysis
- Twenty-three methodologies
- Four stress scenarios
- PDF report, emailed
Five-pack
$120
$24 per report
- Credits never expire
- Compare deals side by side
- Saved property history
- Suited to active acquisitions
Twenty-pack
$400
$20 per report
- Designed for portfolio teams
- Email report templates
- Methodology export
- Priority support
Editorial standards
We publish our assumptions because the methodology is the product.
The composite score is the headline. The assumptions, weightings, and formulas behind it are the work. Both are documented and versioned.
Author and editorial
Built and maintained by Rusty Roof Media. Every methodology is reviewed against published source material before it ships.
Versioned methodology
Every change to the underwriting model carries a date and a changelog. You can see exactly what your report was built on.
No data resale
Inputs you enter are stored only long enough to deliver your report and respond to support requests. We do not sell, share, or aggregate your deal data.
No paid placement
We do not accept fees from lenders, brokers, or property managers. There is nothing to disclose because there is nothing to disclose.