Down Payment Opportunity Cost When Renting or Buying

Start both paths with equal resources

Let buyer upfront cash be down payment plus cash-paid closing and other one-time costs. Let renter upfront cash be refundable deposit plus non-refundable rental fees. Set the shared starting resource to whichever upfront amount is larger. Each path invests only the unused difference. The renter's deposit is not also put in the investment account; if recoverable, it returns as a separate asset at exit.

For example, with 20,000 buyer upfront cash and a 2,000 refundable renter deposit, the renter invests 18,000 initially and receives the 2,000 deposit back at exit. Counting the full 20,000 as an investment and then returning the deposit would give the renter an unearned extra 2,000.

Invest either path's monthly savings

Each month, total the buyer's and renter's complete cash outflows. The common monthly resource is the larger outflow. The cheaper path invests the difference at month-end. If rent exceeds ownership cash cost, buying invests the monthly saving; it is not automatically credited to renting.

With a 1,000 buyer payment and 1,200 rent, no growth, and no other costs, the buyer invests 200 per month. Across 12 months that is 2,400. Under the illustrative zero-rate loan in this cluster, buyer exit assets are 34,400 and renter exit assets are 20,000, a buyer-minus-renter difference of 14,400. Conversely, at 800 rent, the renter invests 200 monthly; the renter's exit assets become 22,400. These are arithmetic examples, not expected market returns.

How the investment balance changes

For each path, new balance = old balance × (1 + monthly return) + month-end contribution. An annual effective return is converted to a monthly rate as (1 + annual return)^(1/12) - 1. Because the contribution is added at month-end, it begins earning returns the following month. The same rule applies to positive and negative returns, as long as the entered annual return remains above -100%.

Test at least a zero-return and a negative-return scenario. Investment balances can fall. An entered return is not a savings-account quote, tax treatment, forecast or product recommendation.

What remains outside the model

The comparison does not automatically calculate investment taxes, mortgage interest deductions, capital-gains tax, inflation-adjusted purchasing power or liquidity risk. A high home-value assumption cannot be treated as a guaranteed return, and an investment rate should never be presented as certain. Review property costs using the ownership-cost guide, then model investing the difference. The housing hub separates this question from affordability.

Frequently asked questions

Sources and scope

CFPB home-budget guidance advises considering upfront cash, ownership costs and other savings goals. Sources checked October 2, 2026. The equal-resource recurrence is CalculatorGeek's declared modeling convention, not a promise of investment performance.