If you only allow short-term debt (say, five years max) then to finance a modern house—even if you could buy it "at cost"—you would need to take out a series of "balloon" mortgages. Every five years you apply for a new loan and use it to pay off the old one. However, this is risky for the borrower since it assumes interest rates won't increase too much (vs. a 30-year fixed mortgage which you can refinance at any time if the rate improve) and that you will be approved for a new mortgage when it's time to pay off the current one.

Or you can save up $1000/mo. for 15+ years so you can pay for the house without taking out a loan… while also paying rent on top of that.