On a recent Rich Habits Podcast Q&A, co-host Robert Croak gave a 40-year-old listener named Angela a blunt answer about the $175,000 she and her spouse netted from a recent home sale. They were weighing whether to throw it at their $475,000 mortgage at 5% or invest it. Robert’s verdict: “I would definitely not pay down the mortgage at 5%. The market’s generally going to perform much better than that over time.”
The stakes are real. Their $3,150 monthly payment eats 37% of their $8,500 take-home pay, and a lump-sum payoff feels like instant relief. Get the decision wrong and you either lock up six figures earning a 5% guaranteed return, or you keep the cash invested and lose sleep every month. The math should drive this.
The verdict: keep the mortgage, fund the bridge
Robert is right, and the spread proves it.
The couple’s mortgage costs 5%. Risk-free alternatives have moved up and are no longer far behind: the 6-month T-bill yields roughly 3.8%, the 1-year T-bill is near 4.1%, and the 10-year Treasury sits at approximately 4.6%. The gap between a guaranteed 5% “return” from prepayment and a guaranteed 4.6% from a 10-year Treasury is now less than half a percentage point. That is the actual opportunity cost of paying off the loan early, and it narrows further once you account for any mortgage interest deduction. Notably, 30-year Treasury bonds have crossed the 5% threshold, meaning patient investors can now lock in yields that match the mortgage rate at the long end of the curve.
Step out of the risk-free lane, and the case for investing strengthens considerably.
The S&P 500 has returned roughly 257% over the past 10 years and about 74% over five years. Robert’s framing makes the point concrete: $175,000 invested at an assumed 9% annual return generates roughly $1,350 per month in growth. That is enough to cover a meaningful chunk of the $3,150 payment indirectly, while the principal keeps compounding. Prepay the mortgage and you crystallize a 5% return forever. Invest it and you keep optionality.
There is a second reason to skip the paydown: liquidity.
The couple’s taxable brokerage holds only $30,000, what Robert calls “the bridge account” for pre-59½ flexibility. Home equity is the worst kind of asset to need in a hurry. You cannot eat drywall, and a HELOC disappears the moment you actually need one.
Who this advice fits, and who it does not
This advice fits Angela’s profile almost precisely: dual income, age 40, a six-month emergency fund, maxed Roth IRAs, employer-matched 401(k), and a 25-year time horizon to ride out volatility. The financial foundation is already built. The $175,000 is true surplus capital.
It fails for a different household: someone with a thin emergency fund, a 7%-plus mortgage, no retirement contributions, or a job in a shaky industry. At a 7% rate, the spread over Treasuries flips, and prepayment becomes the better risk-adjusted call. Context matters too. When the University of Michigan consumer sentiment index sits in deeply pessimistic territory and the personal savings rate is running near 4%, a thin cash cushion is a genuine vulnerability. If your cushion is thin, liquidity beats yield.
What Angela should actually do
Co-host Austin Hankwitz offered a reasonable middle path for anyone who cannot stomach a 37% housing ratio: use a slice of the cash to recast the loan and bring the payment from $3,150 to around $2,800, dropping the ratio to 33%. Their lender allows unlimited recasts with as little as $20,000 down and no fees, making a partial paydown cheap to execute.
- Build the bridge first. Direct the bulk of the $175,000 into a taxable brokerage diversified across broad index funds, since pre-59½ retirement income has to come from somewhere outside the 401(k).
- Park near-term cash in T-bills. A short Treasury ladder currently yields roughly 3.8% to 4.1% depending on maturity, covering 12- to 24-month spending needs without market risk.
- Run a recast only if the payment keeps you up at night. Use $20,000 to $40,000 to nudge the monthly cost down, and invest the rest.
Robert’s call gets the core math right: at a 5% rate with a fully funded financial base, the mortgage is cheap leverage worth keeping in place.
Editor’s note: Treasury yield figures were refreshed to reflect market rates as of July 10, 2026, with the 6-month T-bill near 3.8%, the 1-year T-bill near 4.1%, and the 10-year Treasury at approximately 4.6%; the article also notes that 30-year Treasury bonds have crossed the 5% threshold, narrowing the spread arguments from the original publication.
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