You really aren't talking about the same thing. It's not like you can add 100 housing units to an area one time and achieve affordable housing indefinitely. The

You really aren't talking about the same thing. It's not like you can add 100 housing units to an area one time and achieve affordable housing indefinitely. The housing units have to be added to meet increases in demand. The idea I think you are assuming is that supply causes demand (i.e. demand will always rise to meet supply), and that the supply-demand curve is flat to maintain price regardless of supply.