I have a few spare stables that I don't use. I was approached by a very nice man who I sorta know (we both event, and see each other at shows). He asked me if I'd consider letting him rent a stable and field space. Horse is a quiet TB cross.
I'm a bit iffy about it- I don't need the extra money, and having someone I don't know too well close to my home is making me a bit twitchy.
It would be nice to have someone to ride with though.
There are as many stories of such ending up fine as badly.
Do your due diligence, ask and check out references.
You don't want someone asking to come to your place, no matter what story it gives you, because there was funny stuff going on and was asked to leave.
Once that boarder is vetted out to your satisfaction, get a good CONTRACT, with a liability release clause and a termination one also and be sure it is properly SIGNED before any of his stuff or horses shows up at your gate.
Remember, a good contract is the one that is fair to both sides.
Those are hard to contest if it ever came to that.
Hopefully all will work great and the new boarder will be a real asset to you.