[coolspot]

Homelessness is mostly caused by drugs and/or psychiatric illness.

[dredmorbius]

Expensive and/or insufficient housing doesn't help.

Rich drug addicts tend to remain housed, at least to a greater extent than the poor.

Getting forced onto the streets tends to compound any preexisting tendencies to poor mental health and/or addictive tendencies.

[specialist]

If one first excludes PTSD, domestic violence, health issues, loss of job, and being a homosexual (youth), then -- yes -- the top two causes are in fact the two television tropes which most confirm one's priors.

Well spotted.

[coding123]

Which is caused by falling deep into debt and realizing you won't have a home in a bit.