Affordable housing is a term used to describe dwelling units whose total housing costs are deemed "affordable" to those that have a median income. Although the term is often applied to rental housing that is within the financial means of those in the lower income ranges of a geographical area, the concept is applicable to both renters and purchasers in all income ranges. This article focuses on the affordability of owner-occupied and private rental housing as social housing is a specialised tenure.

http://en.wikipedia.org/wiki/Affordable_housing