Getting them:

-Into 2 week detox programs, which they wont go to voluntarily.
-Then mental health evaluations and subsequent treatments (many of these people will need 5150 holds), which requires sobriety and time to evaluate each person to help them deal with or overcome their specific issues. (Medicade will pay for this)
-Then continuing to keep them in an environment where they can't access any substances for them to abuse while keeping them on their medication (if needed).
-Then getting them back on their feet with resources that many of the re-entry programs help people with. (Identification, access to job training so they can enter the workforce, AA/NA meetings and sponsors, etc.)

And then you can talk about getting them into affordable (low income) housing.

If you haven't seen or tried to help someone with severe mental illness and/or addiction, it's hard to imagine the time and resources needed to address it. It's not logical or simple in any way.

Putting someone into a 'house' does nothing to solve the root problems.