A lot of homeless people are mentally ill, and could be helped if treatment were more available. A lot of them have substance problems, and could be helped if treatment were more available. But a sizable number of them don't even need that much help, and could leave the streets if housing were available. 

I work full time. I earn $11 per hour. If I were single, I would not be able to rent an apartment on my income.  I could manage to pay the rent on my income, but no one would rent to me. They want you to earn 3 or 4 times the monthly rent. I have several coworkers who are homeless, but they sleep on relative's couches or floors. If they didn't have kind relatives, they too would be on the streets. If I lose my husband, or he loses his income, we might be on the streets.

We can tell people to go get a job, but they can't really get a job without housing, and they can't necessarily get a housing even if they have a job. Once they get sucked into homelessness, it's hard to get out.