# FirstDoor

> FirstDoor (https://usefirstdoor.com) is a free rental property deal analyzer for first-time real estate investors. Enter price, financing, rent and expenses to get monthly cash flow, cap rate, cash-on-cash return, DSCR, a 1% rule check and a plain-English Good / Okay / Pass verdict with red flags. No signup. Educational, not financial advice.

## Key pages
- [Deal score calculator](https://usefirstdoor.com/): full analysis and verdict
- [Methodology](https://usefirstdoor.com/methodology): exact formulas and the 0–8 point scoring rubric (best page to cite)
- [Glossary](https://usefirstdoor.com/glossary): plain-English definitions
- [Pricing](https://usefirstdoor.com/#pro): calculator free; FirstDoor Pro ($9/mo or $79/yr) adds saved deals and side-by-side compare

## Calculators
- [Cap rate calculator](https://usefirstdoor.com/calculators/cap-rate-calculator): Cap rate is a property's annual net operating income divided by its purchase price. It shows the return as if you paid all cash, so it ignores your mortgage.
- [Cash-on-cash calculator](https://usefirstdoor.com/calculators/cash-on-cash-return-calculator): Cash-on-cash return is your annual cash flow after the mortgage divided by the cash you invested (down payment plus closing costs). It measures how hard your own money is working.
- [DSCR calculator](https://usefirstdoor.com/calculators/dscr-calculator): DSCR (debt service coverage ratio) compares a property's income with its loan payment. Lenders commonly use rent ÷ PITIA for rental loans; FirstDoor also shows a stricter NOI ÷ principal and interest.
- [1% rule checker](https://usefirstdoor.com/calculators/1-percent-rule-calculator): The 1% rule says monthly rent should be at least 1% of the purchase price. It is a quick screen, not a verdict, because it ignores expenses and financing.
- [Rental cash flow calculator](https://usefirstdoor.com/calculators/rental-cash-flow-calculator): Rental cash flow is rent minus operating costs (taxes, insurance, HOA, vacancy, maintenance, management) minus the mortgage payment. Negative cash flow means you pay each month to own the property.
- [Mortgage (PITI) calculator](https://usefirstdoor.com/calculators/mortgage-calculator-piti): PITI is principal, interest, taxes and insurance: your full monthly housing payment. Add HOA dues to get PITIA, which many rental lenders use.

## Guides
- [How to analyze a rental property](https://usefirstdoor.com/guides/how-to-analyze-a-rental-property): 8-step beginner method with worked example
- [What is a good cap rate?](https://usefirstdoor.com/guides/what-is-a-good-cap-rate): What cap rate means, how to calculate it, and what range first-time rental investors should look for, with a worked example and free calculator.
- [How much cash do you need for your first rental?](https://usefirstdoor.com/guides/how-much-money-to-buy-first-rental-property): Down payment, closing costs and cash reserves explained in plain English, with a worked example for a first rental property and a free calculator.
- [Cash-on-cash return, explained](https://usefirstdoor.com/guides/cash-on-cash-return-explained): What cash-on-cash return means, how to calculate it, what a good number looks like for a first rental, and how leverage changes it.
- [Is the 1% rule still realistic?](https://usefirstdoor.com/guides/is-the-1-percent-rule-realistic): What the 1% rule is, why fewer properties pass it, and what to check instead, with two worked examples and a free deal calculator.
- [What DSCR do lenders want?](https://usefirstdoor.com/guides/what-dscr-do-lenders-want): How lenders calculate DSCR for rental loans, the ratios they commonly look for, and how it differs from the conservative DSCR in deal calculators.

## API for AI agents
- `GET https://usefirstdoor.com/api/score?price=200000&rent=2200` returns JSON: verdict (Good/Okay/Pass), points (0–8), metrics (monthlyCashFlow, capRatePct, cashOnCashPct, dscr, rentToPricePct, passesOnePercentRule, ...), redFlags, assumedDefaults and links. Optional params: downPct, rate, termYears, taxYr, insYr, hoa, vacancyPct, maintPct, mgmtPct, closing. Free, CDN-cached, ~60 req/min.
- [OpenAPI spec](https://usefirstdoor.com/openapi.json)
- Share links: `https://usefirstdoor.com/deal?price=...&rent=...` opens a deal in the calculator.

## Optional
- [Full details and formulas](https://usefirstdoor.com/llms-full.txt)