Ok so someone can relapse even on meds but often the violence is all talk and no action...that doesn't mean you won't have to take action...so actual physical violence is often associated with comorbid drug or alcohol use....if he has issues with that you might want to make abstinence a condition of moving in. Likewise don't give him any legal grounds to remain in your home....explain that if you ask him to leave for any reason he has to leave immediately and his property will be sent after. If you have any issue that makes you uncomfortable and he refuses to leave then call the cops. Basically this policy has no restrictions if he is acting normally but removal from the home if he does anything even suggesting violence. Don't have any obvious weapons around the home either unless they are locked with a code only you know. I suppose it sounds a bit draconian considering he is not likely violent however people are not themselves while psychotic and even people who have been stable on meds have accidentally killed people based on mistaken beliefs. There is typically warning/recurrent psychosis when this happens.