Given the circumstances, it's viable for treatment to come before housing.
The reason we don't house the homeless is a percentage of them destroy whatever is given to them. So, use the treatment process to get them well first.
I may have been too snarky in my original response but my point is this: treatment before housing implies treatment on the street, which I cannot believe is productive. I don't care what meds you take for your schizophrenia, sleeping on the streets is a form of mental assault in itself. If you're trying to beat a drug addiction, the people surrounding you are going to work to undo everything your support groups and methadone clinics are doing for you.
America is obsessed with homeless people proving themselves "worthy" before getting public assistance and it isn't working. Finland has actually been solving homelessness by providing homes first, treatment second.
https://www.theguardian.com/cities/2019/jun/03/its-a-miracle...