In addition to laying out some "rules of engagement" from the outset (perhaps especially including boundaries around private time), I might recommend pre-scheduling some kind of regular check-in routine for you to together discuss what's working (and what's not), so things can adapt/evolve in ways that work for both of you. (You don't want to get into one of those low-grade bad roommate situations where either of you are biding time until the three months are over.)