Saw an interesting post on the City Paper's Housing Complex blog about affordable condos in the Kenyon Square building in Columbia Heights and elsewhere. New condo buildings have some afforable units that are geared towards people making below the median income in the area. However, if those people sell their condos, they only get a fraction of the money back, and they can only sell to other low income people. After 11 years, for example, they get about half back, with the rest going to a city affordable housing fund.
I see the point of these rules, which is to discourage flipping and such, but as the post points out, sometimes people just need to move -- they have a family now or whatever reason. Local nonprofits are looking to change the rules. Interesting stuff.