I had a homeless guy staying with me for about six months when I was single. It was fine except that people thought he was my boyfriend and that we were living together - that’s one of the risks you take, is what people will think of you, and it definitely hurt my job prospects and my social life, so there is that to consider, in addition to the risk of whether they will rob you blind, stash illegal drugs in your house, etc.
In my case the guy was a friend of a friend, and he was an Evangelical Christian, so I knew he wouldn’t drink or do drugs in the house - what he was doing elsewhere may well be another story, but he didn’t do it in the house, which was all I cared about. I didn’t own anything worth stealing at the time; the most annoying part was that it seemed he could eat a week’s worth of groceries at a single sitting, and my grocery bill was the highest it’s ever been - even with a husband and kids, I still don’t spend what I spent on that guy.
Once he got his feet on the ground, he left and we lost touch.