Honest, non-snarky answer... to be pedantic, for me it's not a question of affordability. I'm a software professional with a very good income, and I could do it on my own.

I have a friend a few months younger than me. She makes less than $15k/year, and has two children living at home. Under those financial circumstances, she has totally paid off her home, which should tell you how frugal and responsible she is. She has also experienced extensive hospitalization due to illness. If she had to pay for that (it was paid for by state-subsidized health care), she'd have lost her house.

edit: Medical costs are the leading cause of bankruptcy in the US.