Affordable housing is housing which is deemed affordable to those with a household income at or below the median as rated by the national government or a local government by a recognized housing affordability index. Most of the literature on affordable housing refers to mortgages and a number of forms that exist along a continuum – from emergency homeless shelters, to transitional housing, to non-market rental, to formal and informal rental, indigenous housing, and ending with affordable home ownership.

Homelessness or houselessness – also known as a state of being unhoused or unsheltered – is the condition of lacking stable, safe, and functional housing. The general category includes disparate situations, such as living on the streets, moving between temporary accommodation such as family or friends, living in boarding houses with no security of tenure, and people who leave their domiciles because of civil conflict and are refugees within their country.