One way to look at "affordable" is to think "right sized" which excludes
ALL of the McMansion's & Suburbia built in the last 25>30+ yrs.
"Right sized" is smaller and more energy effecient while still being a good shelter.
All one has to do to see "right sized" is look at home built before 1970's when the
housing flipping maddness started. People in the 70's and on almost always built, or
bought, a house not so much to live in as to profit from based on the ever upward
house of cards profits that all expected to get. Those of us who bought older homes
to "live in" rode over the craziness of the housing market.
So in order to come close to understanding "affordable" one must first understand
"right sized". Anything else is a fools game.