Bluebell, I have seen it on this board many times, our difficult child's are wildly resourceful "out there" they can live on air when they want to. All our parental fears are rarely realized, for they use their incredible skill at manipulation and conniving, lying and stealing, lack of empathy and lack of responsibility as well as their 'charm' when they want to use it and remarkably find ways to survive.
And, so you know, I have a good amount of mental illness in my family. My brother is schizophrenic who at one point lived on the streets in L.A. for many years. He preferred that until he got older and he moved into a sort of flop house, but amazingly, he survived okay. A number of our members here have kids who are presently homeless or have been homeless and so far, they have all gotten through.
You may already know about NAMI, (the National Alliance on Mental Illness) but if you don't, they can be accessed online and they have chapters everywhere. They have very, very good courses for parents and resources for you and possibly for your son too. It would be worth a phone call to them. Their parent courses are very helpful for US.
It's so very hard to live with a child who acts out in the way your son does. I am very glad you're here, hang in there, keep posting, it helps a lot.