What is the cause of homelessness in Houston?

You try to pretend like it's a normal part of every day life to see someone essentially walking like a zombie walking past high-priced commercial real-estate and million-dollar condos completely spazzed out and barely able to stand on two feet. It's not. If you've ever driven or walked through certain parts of downtown, midtown or east downtown, then you know what I'm talking about. Certain parts of downtown are essentially taken over by homeless. This is not a judgy post. I honestly want to help as a regular citizen but I don't know how. It's probably not a matter funding because it'd have been fixed already if that was the case. Houston is a pretty affordable city so what explains this?

What is the cause of this and how can regular people help? Is it because of gentrification(EaDo, 4th ward, 3rd ward, etc)? Also why are they so disproportionately male and disproportionately black? Is this related to the gentrification point? If so this is an externality of housing policy and growth that's perhaps not being addressed. Are they mostly from Houston or did they come from out-of-state? Do most suffer from mental problem or drug problems or are ex-cons? A lot of them look pretty beaten up but some look able-bodied but maybe just haven't gotten a break from the cruel game of life.

Random point but I was driving to UofH three weeks ago and I noticed in 3rd ward with regards to all the construction and even city-related work, most of this work was doing by illegals(not stereotyping but it was pretty obvious) – this is in a predominantly black neighborhood where there is above-average unemployment.

Are illegals/undocumented easier to control(probably the wrong word here) – is that why this was the case?