[Retric]

In these situations inflation is your friend. Assume 2% inflation and 5 years chips away at ~10% of cost of servicing a loan. AKA 40% of your income = 36% in 5 years and 32% in 10 years. Get 3.5% and that's 33% in 5 years and 28% in 10 years.

[allwein]

You're of course making the assumption that his income would keep pace with inflation, which sadly has not been true for a large percentage of the American population lately.