In any form, homelessness happens because people cannot access the housing and supports they need. This can be the result of economic and socio-structural factors, like shortage of affordable housing, extreme poverty, and discrimination; it can occur when systems of care and support fail; and it can occur in response to individual or relational factors, such as relationship violence or personal trauma.

The immediate cause is often an exogenous shock, such as a health crisis, unexpected lack of employment, or abrupt housing loss due to eviction or domestic violence. But socio-structural factors make certain people especially vulnerable, and gaps in the social safety net and homelessness services systems can extend homelessness or make it more difficult to remain housed.