🏛️ IRS Official Publications
The foundation of all tax and depreciation calculations. These are the authoritative IRS sources.
https://www.irs.gov/publications/p527
Used for: Residential rental property depreciation (27.5-year recovery period), mid-month convention, land vs. building allocation, and what improvements are depreciable. Tab 4 (IRS Depreciation Calculator) follows Pub 527 formulas exactly.
https://www.irs.gov/publications/p946
Used for: General depreciation rules, bonus depreciation, Section 179 expensing, and listed property rules. References the Modified Accelerated Cost Recovery System (MACRS) which governs all U.S. property depreciation.
https://www.irs.gov/taxtopics/tc701
Used for: Understanding tax-deferred like-kind exchanges for real estate. The upcoming Tab 8 (1031 Exchange) will model deferred gain calculations based on IRC § 1031 rules. Note: after the 2017 Tax Cuts and Jobs Act, 1031 applies only to real property (not personal property).
https://www.irs.gov/taxtopics/tc415
Used for: Passive activity loss rules, hobby loss rules, and what rental expenses are deductible. Tab 4 references Topic 415 for taxable income after depreciation.
🛡️ Federal Consumer Protection Resources
https://www.consumerfinance.gov/
Used for: Mortgage disclosure rules (TRID), APR calculations, and understanding loan estimates. The cash flow calculator's mortgage payment formula follows standard amortization used by CFPB-compliant lenders. Also references CFPB guidelines onAbility-to-Repay and Qualified Mortgages.
📊 Industry Research & Market Data
Market benchmarks and rent trends are sourced from these industry-leading research organizations.
https://www.nmhc.org/research-insight/
Used for: Cap rate benchmarks by market (national average ~5.5% per NMHC 2024), multifamily rent growth trends, and vacancy rate averages. The benchmark comparison in Tab 1 references NMHC market data.
https://www.costar.com/
Used for: Commercial real estate market trends, multifamily sales comparables, and rent growth data by metro area. Referenced in the methodology for multifamily (Tab 5) and BRRRR (Tab 2) ARV estimation guidance.
https://www.freddiemac.com/pmms
Used for: Weekly average mortgage rates for 30-year fixed loans. The default interest rate in calculators references recent PMMS averages. Users should enter their actual quoted rate for accurate results.
https://www.nar.realtor/research-and-statistics
Used for: Median rent trends, housing affordability indices, and existing home sales data. Referenced for market context in the long-term rental (Tab 1) methodology and blog articles.
🏖️ Short-Term Rental (STR) Market Data
https://www.airdna.co/
Used for: STR occupancy rate benchmarks (US national average ~55% per AirDNA 2024), average daily rate (ADR) by market, and RevPAR trends. Tab 3 (Airbnb/STR) uses these benchmarks for the occupancy rate default and market comparison. Users should verify with local Airbnb/VRBO comparables.
✅ How to Verify Our Methodology
Transparency means you can verify every claim. Here's how:
1
Check the IRS sources: Click any IRS link above. Publication 527 and 946 are free, public documents. Verify that our depreciation formula matches the IRS straight-line method.
2
Cross-reference market data: Visit NMHC.org and CoStar.com to verify cap rate averages and rent growth figures for your target market.
3
Test with your CPA: Show the depreciation schedule from Tab 4 to your CPA. Ask if the straight-line calculation matches what they would file on IRS Form 4562.
4
View page source: All calculator logic runs in your browser. Right-click → "View Page Source" to see the JavaScript. No black boxes.