A Free FIRE Calculator That Actually Models Rental Income (ProjectionLab and Boldin Alternative)

Every FIRE calculator can compound a stock portfolio. Almost none of them know what to do with a duplex. That is a strange gap, because for people starting from a low income, rental property is often the fastest working lever: it cuts your biggest expense while adding income that grows with rents. The projector below treats rental property as a first-class part of the plan instead of a footnote.

It runs your numbers two ways at once — investing only, and investing plus a house hack — and tells you how many years the property moves your financial-independence date. It is free, needs no signup, and your scenarios save in your browser so they are still there next visit.

Prefer a full page: open the FIRE projector here.

Why rental income bends the math so hard

The standard FIRE target is your annual spending divided by a withdrawal rate, usually 4%: spend $40,000 a year and you need roughly a $1,000,000 portfolio. Durable rental income attacks that target directly. Every $100 a month of cash flow is $1,200 a year you no longer need the portfolio to produce, which at 4% shrinks the target by $30,000. A modest house hack producing $200 a month while you live there, and $1,100 after the mortgage is gone, removes hundreds of thousands of dollars from the finish line — on top of the housing cost it frees up for investing every month along the way. That double effect (smaller target, faster saving) is what the side-by-side scenarios make visible.

What the paid planners charge for

The polished FIRE planners are good software, and for complex situations they earn their keep. But the pricing, as of July 2026, looks like this: ProjectionLab’s free tier now saves your plan between sessions (a change they shipped in April 2026); the deeper cash-flow and tax analysis starts at the Premium tier around $129 a year. Boldin (the planner formerly called NewRetirement) keeps real estate and rental modeling in its paid PlannerPlus tier, about $144 a year after a price increase announced this July. WealthTrace starts north of $229 a year with no free tier at all. Meanwhile the free classics (cFIREsim, FICalc, FIRECalc) are excellent at portfolio simulation and treat rental income as, at best, a flat “other income” line that never grows and never has a payoff date.

That last row of honesty matters: if you want Monte Carlo simulations, tax-aware withdrawal ordering, or estate planning, the paid tools do things this one does not try to do. What they should not get to charge for is the basic question a beginning house hacker actually has: does buying this duplex move my freedom date, and by how much.

How to use it well

Feed it honest property numbers. The rental cash flow and the housing cost you save both come straight out of the House Hack Calculator — run a real listing there first, then carry the two figures over. Use returns after inflation (5% real is a common planning assumption for a diversified portfolio) so the answer reads in today’s dollars. And treat the withdrawal-rate box as the philosophical dial it is: 4% is the classic rule of thumb from the Trinity study line of research, 3.5% is the cautious version for longer retirements.

If the projector says the house hack moves your date by years, the next question is readiness — the Readiness Roadmap turns your current finances into a phased plan. And if you are earlier in the journey than that, here is how much money it actually takes to start.