President Trump, comparing himself to President Franklin D. Roosevelt (FDR) over the weekend, proposed the potential for a 50-year mortgage in a bid to lower housing costs. I'm no economist, but even I know that's actually a terrible idea. Here's how bad it is by the numbers.

FDR originally proposed the idea of the 30-year mortgage. That's where Trump's comparison on Truth Social comes from as he looks for a quick fix to borrowing pain under his presidency.

Before Franklin D. Roosevelt reimagined the American mortgage, home loans were short, brutal affairs. Borrowers usually had to cough up half the cost of a house up front and pay off the rest within five to ten years—often with a giant “balloon” payment at the end. The Great Depression crushed that model. FDR’s New Deal created the modern 30-year mortgage, spreading payments over a generation and turning home ownership into a cornerstone of middle-class life.

Donald Trump, never shy about invoking historical parallels, recently posted an image likening himself to Roosevelt—claiming he’d take the idea further with a 50-year mortgage. It's basically a sugar hit for housing affordability. Extending repayment terms effectively lowers monthly repayments, giving the illusion of cheaper housing without cutting interest rates. It’s like an artificial rate cut he can deliver himself, sidestepping Jerome Powell and the Federal Reserve entirely. For struggling homeowners, that sounds appealing: smaller monthly payments, bigger budgets, and less immediate pressure. But as with most financial sleight-of-hand, the short-term sugar hit hides a long-term cost that can hollow out household wealth.

Stretching a mortgage from 30 to 50 years might sound like a ticket to affordability, but it’s a quiet disaster for your bottom line. The extra 20 years don’t just tack on more time. they stack on hundreds of thousands of dollars in interest payments. Banks would make out like bandits while homeowners spend decades feeding the machine.

By the numbers: how much extra it would cost you

To see what it might look like in Australia, take the current average home loan of $678,000. At 5.6%, a standard 30-year term would mean monthly repayments of about $3,880. Stretch that to 50 years and repayments drop to roughly $3,450—a tidy $430 less per month. But over the full term, the total interest balloons from about $723,000 to more than $1.4 million. That’s an extra $700,000. Almost the price of another house in some markets. And it's paid directly to the bank's bottom line for the privilege of “saving” a few hundred dollars each month.

It’s the kind of policy that looks generous in the first year, then quietly robs you every year after.

Let's hope the banks aren't listening

In theory, a 50-year mortgage could ease pressure on younger buyers locked out of the market by high prices and stagnant wages. It’s a political answer to an economic problem. Stretch the timeline and, voilà, affordability.

But in practice, it risks trapping a generation in near-permanent debt. Few Australians keep the same home for 50 years, so borrowers could find themselves paying almost nothing off the principal in the early years, leaving them vulnerable if prices fall or they need to sell.

And then there’s the equity problem. With such long horizons, most repayments go straight to interest, not ownership. It could take decades before homeowners build meaningful equity, especially if housing values cool. That means less security, less flexibility, and more dependence on rising property prices to bail them out. It’s a slow grind toward ownership, not a pathway.

Financial regulators would likely balk at the idea. Australia’s 30-year standard wasn’t chosen at random—it balances affordability with fairness between borrower and lender. A 50-year loan tips that balance decisively toward the bank. The numbers make it clear: while a stretched mortgage looks friendly to the struggling buyer, the only guaranteed winner is the lender who gets to collect 20 more years of interest.

So when Trump says he wants to be the new FDR of housing, it’s worth remembering what made Roosevelt’s idea revolutionary. The 30-year mortgage was designed to make homeownership possible. A 50-year mortgage, by contrast, would make it perpetual.