What they do is they sell a dollar for 1.07$ future dollars (and, realistically, less than that because of defaults but whatever).

It's a lot more than $1.07 future money, a mortgage is more like $2 or these days $5

If you're offering even 25 year 75% LTV mortgages at such a low interest rate it's $1.07 future money you're going bankrupt. And these days people are taking 30 year, 95% LTV or even asking for 40 year 100% LTV which is fully batshit.