House Hacking Calculator

What House Hacking Actually Means in the Military Context

House hacking is the strategy of buying a property — typically a 2-4 unit residential property — occupying one unit yourself, and renting the other units to tenants whose rent covers most or all of your mortgage. For service members, the math is uniquely attractive because of two factors civilians don't share:

• VA loans permit 0% down on 2-4 unit primary residences. Conventional financing typically requires 25-30% down on multi-unit investment properties. The VA program treats the same property as a primary residence (because you're going to live in one of the units), unlocking the 0%-down structure.
• BAH covers the unit you occupy regardless of ownership. BAH is paid based on rank, dependency status, and ZIP — not whether you rent or own. When you house hack, BAH effectively pays the mortgage on your unit, while tenant rent covers the rest of the building.

Combined, these two factors mean a service member can often acquire a cash-flowing rental property with little or no out-of-pocket cost beyond the inspection and closing. That doesn't mean every deal works — most don't — but the deals that do work are usually dramatically better than what civilians can replicate.

VA Loan Rules That Matter for House Hacking

The VA Home Loan program has specific rules you have to thread:

• 2-4 unit cap. VA loans permit duplexes, triplexes, and fourplexes. Five-unit-plus properties are commercial financing regardless of borrower. Single-family homes with an ADU may or may not count as a 2-unit — the lender's underwriter decides based on legal classification.
• Owner-occupancy requirement. You must occupy one of the units as your primary residence. The standard expectation is at least 12 months of occupancy, with limited exceptions for PCS orders that relocate you sooner. This is enforced — taking a VA loan for a property you never intend to live in is loan fraud.
• Self-sufficiency rule for 3-4 unit properties. On triplex and fourplex purchases, the property must be "self-sufficient" — meaning the projected rental income from all units (including the one you occupy) covers the full PITI. The lender hires an appraiser to determine projected market rents. If the property fails self-sufficiency, the VA won't finance the deal.
• VA funding fee. A one-time fee set by 38 USC § 3729(b) and varying by service component, down payment tier, and first-vs-subsequent use. The calculator above picks the correct tier automatically. Veterans with a VA-determined disability rating of 10% or higher are exempt entirely under § 3729(c).
• Entitlement. Each veteran has a finite VA entitlement amount; using it to buy means you can't use the same entitlement for another VA loan until it's restored. Service members who plan to PCS and house hack again at the new station should understand restoration timing before the first purchase.

The Honest Cash-Flow Math, Step by Step

The honest cash-flow math for a house hack starts with PITI and works outward — and crucially, includes reserves. The previous version of this calculator showed a "cash flow" number that ignored reserves entirely, which made nearly every deal look profitable on paper. The rebuilt calculator subtracts reserves from the headline, so the number you see is genuinely the "does this deal carry cushion" number, not the "does this deal pencil before anything goes wrong" number.

1. P&I. Principal and interest, set by the loan amount, interest rate, and term. The VA loan's edge is no PMI — that's real money, often $200-$500/month vs. a conventional with the same down payment. The calculator falls back to linear amortization at 0% interest so it doesn't divide by zero.
2. Property taxes. Vary wildly by state and county. Texas runs 2-3% of assessed value per year; California is closer to 1%; most other states are between. Verify with the county assessor website before assuming.
3. Hazard insurance. Multifamily properties cost more to insure than single-families. Get a real quote, not an internet estimate. Flood-zone properties add flood insurance on top.
4. HOA dues. If the property is in an HOA, monthly dues come straight off net position.
5. Maintenance reserve (default 8% of rent). Tenants break things; your roof leaks; your HVAC fails. The default 8% is an industry rule of thumb — older properties often need 12-15%.
6. Vacancy reserve (default 6% of rent). A unit empty 1 month out of 14 is roughly 7% vacancy without unusual circumstances. The default 6% is mid-pack — high-turnover markets run higher.
7. Capex reserve (default 5% of rent). A sinking fund for the major systems (roof, HVAC, water heater, appliances) that wear out on a 10-25 year cycle and cost five figures when they go.
8. Property management (default 0%, post-PCS 8-10%). If you self-manage during your owner-occupancy period and plan to hire out post-PCS, model both scenarios.

The Net Monthly Position is gross income (BAH + tenant rent) minus PITI minus all reserves. If positive, the deal carries cushion. If negative — even slightly — the deal has no margin for the things that always go wrong.

When the Math Actually Works

Three patterns reliably produce house-hack deals that pencil:

• Affordable markets with 2-4 unit inventory. Many Texas cities (San Antonio, Dallas, Killeen near Fort Cavazos), North Carolina (Fayetteville near Fort Liberty, Jacksonville near Camp Lejeune), Georgia (Columbus near Fort Moore), and Oklahoma still have duplexes/triplexes priced where the math works. Run the calculator with current MLS comps.
• Properties priced below replacement cost. Older multi-unit buildings in established neighborhoods often trade significantly below new-construction replacement cost. Plan on higher reserves for older mechanicals, but the entry math is better.
• Mid-rank service members with stable orders. E-6/O-2 and up tend to have BAH levels that make the math work in most markets, plus enough income stability to handle a tenant turnover or a major repair without crisis. Junior enlisted with no emergency fund should think hard before house hacking.

Three patterns reliably don't work:

• High-cost coastal markets. Coastal California, Hawaii, and the New York/New Jersey corridor have 2-4 unit pricing that's been bid up beyond what BAH plus market rents can support. The math rarely pencils even with 0% down.
• Buying near a soon-to-close base. BRAC announcements destroy local rental demand. If the base is on a drawdown list, the cash-flow assumption can collapse the year after closing.
• Buying right before a known PCS. If you're already on orders to leave in 6 months, you can't satisfy the 12-month occupancy requirement comfortably. Wait for the next station.

Managing the Property After PCS

The strongest house-hack outcomes come from holding the property long-term as a pure rental after you PCS. When you leave, the unit you occupied also goes to a tenant; all units now produce rent; BAH becomes BAH at the new station for your new housing decision.

• Find a property manager before you're overseas. Self-managing from across the country, much less from Korea or Germany, is a recipe for late maintenance and irritated tenants. Property management fees of 8-10% of rent are usually worth it.
• Document the property condition at PCS. Photos and walk-through video before tenants take over the unit you occupied. This protects against later disputes about pre-existing wear and damage.
• Plan for the tax filing. Once you're renting all units, you file Schedule E. Depreciation, mortgage interest, property tax, and direct repair costs are all deductible. Many house-hackers find their first year as a full landlord generates a significant tax shield via depreciation alone.

How This Calculator Works

Every value flows through the platform's data layer — no hardcoded rates that age in code:

• BAH — DFAS BAH rates auto-ingested into the platform's bah_rates table. Type your duty station to autofill; override manually if you're modeling a different ZIP.
• VA funding fee — 38 USC § 3729(b) statutory schedule. The calculator picks the correct tier from your service component (regular vs. Reserve/Guard), down payment percentage, and first-vs-subsequent-use status. The disability waiver toggle implements § 3729(c).
• Reserve % defaults — Industry conventions (8% / 6% / 5% / 0%) exposed as user-overridable sliders. Not statutory and not auto-refreshed.
• Mortgage payment — Standard fixed-rate amortization formula, with linear-amortization fallback at 0% interest so the calculator never divides by zero.
• VA loan limit advisory — Annual FHFA baseline from the platform's SSOT. Veterans with full entitlement face no statutory limit since 2020; the warning is for partial-entitlement borrowers.

The Net Monthly Position headline subtracts reserves. This is a deliberate design choice — the previous "Cash Flow" label implied cash-in-pocket, which the math never produced because reserves weren't in it.

Related Garrison Ledger Tools

• PCS Planner — When PCS converts the house-hack into a pure rental, model the move costs and the BAH change at the new station.
• TSP Calculator — Real estate vs. TSP-only retirement math; many service members build wealth through both.
• Salary Calculator — Total compensation including BAH, the cornerstone of any house-hack analysis.
• Ask the Military Expert — Five free questions a month with citations from VA loan rules and BAH publications. Great for the "but in my specific situation" questions.
• Monthly Military Financial Briefing — Rate moves, BAH releases (December), and the rent-vs-buy planning notes military families actually use.

Sources

VA Home Loan program · VA funding fee schedule (38 USC § 3729) · VA loan limits (FHFA) · VA Pamphlet 26-7 (Lender's Handbook) · VA Certificate of Eligibility (COE) · Official DoD BAH calculator · IRS Topic 414 (Rental Income and Expenses)