Welcome to our forum.
You have the right idea in considering that seeing something in practice could be tougher than knowing something in theory, although it is also possible that A and J will move in and you'll find that you have no problems at all, and if so, that's great.
Privacy could be an issue. There may be times when you need to "retreat into your cave" sometimes and detox, so it could be helpful if you have your own space for that. It is also unknown if J's brain surgery will affect his mood or behavior in any way.
Mostly I just suggest to continue reading threads here, and post if you have any thoughts, questions, or concerns. Bipolar can be a tough nut to crack (I know that by experience), so you will probably have to deal with that and its effects in a new environment.
I am sure you will make some good friends here, this is a good site to visit. Glad to have you aboard.
Love means never having to say, "Put down that meat cleaver!"