I had a singer that was fresh from Betty Ford, started playing with him about 4 months after he got out.
He had the guitarist mainlining cocaine within about 7 weeks.
Not exactly the same situation, but generally folks in that kind of transitional phase are not going to be super reliable. They may or may not also be looking to relapse with a new "buddy"/drag someone down with them, so that can be problematic if there's anyone else in the band that's impressionable.
As always YMMV.
Also, I've been around meth abusers, if you're not doing that yourself and/or do not have extensive experience with them, this will probably get messy. I'm assuming you fall into one of those categories as "5 years in prison for meth" didn't send you running to the hills already.
I have seen a number of folks get caught in that particular trap, and even the ones that pull themselves out, and appear ok for years, can have occasional relapses. So, even if he wants to be clean....there's a pretty big chance there will be downstream problems.
If this was pot or something I'd tell you to laugh it off (and you probably wouldn't even post over that.) Heroin and meth though are really, really nasty drugs that get their hooks pretty deep into their abusers. If you haven't had personal experience with the depths that folks in that situation can sink to, it's probably best to stay away.