America’s 25-year-olds, listen up. You’re probably thinking how perfect it is that a $1,400 “stimulus” check—a lot more if you’re married with children—is arriving just in time to celebrate the great reopening. You’re grateful to our new President for funding a long weekend on the Florida beaches, backyard swings for your kids, or even paying off your credit card. But be warned that the spending onslaught that’s bringing you that windfall is part of a blowout that will effectively saddle you and your spouse with almost $150,000 in federal debt when you reach 35 in 2031. That nut might be as big as the loan on your starter house.

Even if interest rates stay incredibly low, your household’s annual share of the payments will be about $1,750. That’s not just for one year. Those bills will go on forever and keep growing in size. And don’t think that the Treasury can just keep piling all that ballooning interest on the federal credit card. A decade from now, the U.S. could be grappling with debt that’s one-and-a-half times the size of the economy, dwarfing the current burden in Italy. Washington can raise the extra cash only by paying stiff rates, meaning your bill could swell to $3,000 a year when you’re 45. Chances are good that you’ll be paying for the Biden agenda either in far higher taxes or spiraling inflation that keeps the price of groceries rising as fast or faster than your paychecks.

As a candidate, Biden proposed $11 trillion in new spending, and in his first six weeks in the White House, he hasn’t withdrawn any part of that platform. The dozen measures listed in his campaign manifesto include a $2 trillion climate and infrastructure initiative, the latter titled Build Back Better; $1.5 trillion in aid for colleges, K–12, and preschool; $1.4 trillion for expanding the Affordable Care Act, adding a public option, and bolstering long-term-care assistance; $1 trillion in additional Social Security and Supplemental Security income; and $550 billion in family-leave funding.

Biden also pledged a “Heroes Act” earmarking $3 trillion to lift the economy from the ravages of COVID-19. On March 6, the Senate passed the first part of the “stimulus,” the $1.9 trillion coronavirus relief bill that includes the wildly popular $1,400 payments. Biden has said nothing about about lowering the spending target in the Heroes Act proposal. More pandemic-related spending is likely to follow. Enhanced unemployment benefits, for example, expire in the late summer, and it’s a good bet Biden will push for another extension. Hence, we’ll assume that the total $3 trillion in emergency expenditures will happen.

The Biden agenda is heavily front-loaded. The $3 trillion stimulus is designed to be spent in the next couple of years, and the President pledged to lavish the full $2 trillion in infrastructure and green energy by the end of his term in early 2025. So I’ll assume that all $5 trillion must be borrowed over the next four years, and that the additional $6 trillion will come in relatively equal increments in the 10-year span from 2021 to 2030.

Biden is also promising big tax increases that he claims will raise an extra $3 trillion over the next decade, including hikes in corporate income levies, the top tax rate for individuals, and an almost-doubling of the capital gains rate for high earners. The nonpartisan Tax Policy Center forecasts a lower figure of $2.1 trillion for tax revenues, and I’ll use that estimate. By spending an additional $11 trillion above the CBO’s forecasts, and collecting $2.1 trillion more in revenue, the Biden agenda would add approximately $9 trillion to the federal debt, excluding interest on all those borrowed trillions.

Using the CBO’s most recent budget projections over the coming decade released in February, we’ll predict that annual rates on the federal debt will average 1.8%. That’s an extremely modest estimate. In reality, the number is wildly unpredictable, and could be much higher. Government bond yields are jumping right now, a trend the CBO didn’t predict in its February report. Since the start of 2021, the yield on the benchmark 10-year Treasury spiked from 0.93% to almost 1.60%.

If rates do remain as slender as the CBO forecasts, interest on the spending blowout would come to $1.4 trillion, lifting total debt by $10.4 trillion (the $11 trillion net of the $2 trillion in tax increases, or $9 trillion, plus the $1.4 trillion in interest).

The CBO also posits that average interest on the federal debt will reach 2.4% by 2031. Once again, that’s a highly optimistic outlook. In January 2019, the CBO expected a 3.2% burden by 2029, underscoring how much these projections move around. By 2030, the number of U.S. households is expected to rise from 122 million to around 144 million. The extra annual interest that’s a legacy of the Biden agenda would equal that $1,750 per household. Once again, that’s assuming rates remain extremely subdued versus history. The CBO reckons what the government pays as borrowings explode will march steadily to around 5% over the following two decades. “Piling on the additional trillions in debt makes America’s margin for error on interest rates very small,” says Brian Riedl of the conservative Manhattan Institute. An unforeseen spike, he warns, could swamp the budget with much higher payments.

The best bet is that rates will indeed be much higher than projected well before 2030 or 2031, and that the bill for each household will far exceed $1,750 in a decade. Everett Dirksen, the hard-drinking, gravelly-voiced Senate minority leader from 1959 to 1969 was a deficit hawk who famously joked, “A billion dollars here, a billion there. Pretty soon it adds up to real money.” Today, lawmakers talk about spending extra trillions as if Uncle Sam is flush and can easily afford it. But those trillions are real money, and Uncle Sam will eventually tap out his credit card. Then it’s the middle class, the folks so delighted over those stimulus checks, who’ll have to pay. And pay, and pay.