Home Affordability SimulatorBuy the house without giving up early retirement

How big an emergency fund do home buyers really need?

The generic advice — three to six months of expenses — was not written for the person who just wired most of their liquid net worth to a title company. A home purchase concentrates three risks into the same short window: your savings hit their lowest point in years, your monthly obligations jump, and the layoffs that could interrupt your income cluster in exactly the market conditions that would also mark down your remaining investments. So the question isn't "how many months feels responsible" — it's what a buffer is measurably worth. Here's the measurement: one household for whom the purchase is a genuine stretch ($90,000 income buying a $520K house), identical in every way except the cash left over after closing, a thousand simulated futures each.

What the leftover cash is worth

That is not a subtle effect. The first three months of buffer cut the ruin rate from 13.7% to 5.1%; six months cut it to 1.2% — roughly a tenth of the bare-closing figure — because six months covers the single most common disaster shape in the simulation: one layoff, about 6 months without income, arriving in a down market where selling investments means selling low. Beyond a year, the marginal month buys almost nothing; the cash starts costing more in forgone compounding than it saves in ruin risk. The curve has a knee, and the knee is early.

Two honest footnotes

The buffer buys survival, not retirement. This stretched household's odds of financial independence on schedule are poor at every buffer size — the purchase price did that, and no emergency fund undoes it (the house-poor anatomy is that story). Conversely, a comfortably-priced purchase barely trips the guardrail even with a thin buffer — the planner's well-padded default household posts a near-zero forced-sale rate throughout. The buffer question is really the price question wearing a disguise: the more you stretch, the more months you need behind you.

"Expenses" means the post-purchase number. Not your rent-era budget: total carrying cost plus living costs — mortgage, property tax, insurance, maintenance, and everything else. An emergency fund denominated in your pre-purchase budget is quietly a third too small on the day the obligations jump.

Where to keep it, and how to find your own knee

The buffer's job is to exist at the exact moment markets are down — which is why it lives in cash or equivalents, not in the portfolio it's protecting. Sizing it is a computation, not a feeling: run your scenario, set your real liquid savings, and watch the forced-sale rate as you move the balance up and down. The point where the curve flattens is your number. If a layoff in your field means twelve dry months rather than six, the model has a dial for that too — and it moves the knee exactly as far as you'd fear. Deciding the down payment and the buffer together? The down-payment guide runs that trade with the same machinery.

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