Guides

The simulator answers your question with your numbers. These essays cover the ideas underneath it — what the usual affordability shortcuts get wrong, and what a model that simulates thousands of futures can see that a ratio can't.

• Why the 28% rule misleadsPayment-to-income rules can't see savings rates, taxes, market risk, or your retirement timeline. Two households the rule treats identically can have wildly different odds of staying on track.
• Sequence-of-returns risk is a home-buying problemThe order of market returns matters most right after you drain your taxable account for a down payment. Why the same average return can leave one buyer fine and break another.
• Rent vs. buy is the wrong questionThe interesting question isn't which tenure wins on average — it's whether a specific purchase price keeps your plans intact in the futures where things go wrong.
• How a house purchase moves your FIRE dateA home changes both sides of the financial-independence equation: it raises the portfolio you need and slows the rate you build it — but it can also retire your housing bill. How to think about the trade.
• What a mortgage rate actually does to what you can affordThe same household, simulated at rates from 5% to 7.5%: how each half-point moves the highest price that still leaves retirement on track. The answer is bigger than the payment change suggests.
• 10% down vs. 20% down: what the simulation saysA bigger down payment buys a smaller payment and no PMI — but it also drains the buffer that carries you through a layoff. The same purchase simulated at 10%, 20%, and 30% down.
• What "house poor" actually looks like in the numbersHouse poor isn't a payment ratio — it's a set of futures: the vacation fund that becomes the furnace fund, the portfolio that stops growing, the layoff that forces a sale. A simulated anatomy.
• How big an emergency fund do home buyers really need?The months right after closing are the most fragile of the whole plan: savings drained, costs up, and layoffs correlated with crashes. What the simulation says a cash buffer is worth.
• Should you wait to buy? The arithmetic of timing the housing marketWaiting for lower rates or lower prices is a bet with a carrying cost: rent paid, appreciation missed, and a savings race against the market. How to price the wait instead of guessing.