You take the difference between rent and ownership costs, not just the down payment, leverage that (2x max), and calculate the difference. The Times has a good tool for this [1]. (It doesn’t lever. Securities-based loans are almost always cheaper than mortgages.)
The sucker in the present math is the individual, aspirational, emotionally-motivated buyer. The winner, the sellers and first-lien lenders.
> assuming your rent doesn’t go up?
I’d actually argue this is what most people pay for with homeownership. You may become a bit poorer, but your future is more certain. If you’re savvy you can use that certainty to take more risk in other parts of your life. Buying a home, for most Americans, is buying insurance. The problem is few see it that way, which is pretty great for the real estate industry.
[1] https://www.nytimes.com/interactive/2024/upshot/buy-rent-cal...