Earlier quoted context omitted.
I feel like $80k must be an outdated number. My wife and I pull in just under $100k together, and we can't even (comfortably) afford a home. Between rent, student loan payments, health insurance, bills, and car loans, and food, I think we maybe have $500 left to throw around each month. If we were paying against a mortgage, that would basically be zero.
It's definitely outdated, or at least location dependent. The average rent in Manhattan in 2/16 was $3,850. Landlords won't rent to you unless you earn 40x the monthly rent which is $154k. In Brooklyn, the average is $2,716 which ends up being $108,640. ( http://www.mns.com/brooklyn_rental_market_report )
The most financially effective way to be a programmer is to work remotely for someone who pays SF or NYC salaries and live in a moderate COL area.
I've always seen the rental income requirement you stated phrased as "monthly income must be at least 3x monthly rent", in case the 40x thing threw anyone else off (40/12=3.33).