Marth + Link are my Melee mains - Whatever Link it is, they are going to be traveling around the world. If not, they'd probably be trying to collect everything in whatever video games we have and be super try-hard. That could be fun, but the lack of talking would be a problem. Marth seems like an awesome person to live with though. Very nice and polite (or at least, I assume that's what he's like).
Cloud and Charizard were temporary Smash 4 mains - I'd imagine them both being really apathetic towards everything. Would have to work harder to make enough money to feed them I'd imagine. I dunno if Cloud could handle a job that doesn't involve destroying things and Charizard can't really enter any tournaments to test his might.
All my other "serious" considerations for mains for Ultimate. Yeah it's been hard narrowing it down -
Chaos, just absolute chaos.
I don't even think my house could fit everyone, especially Ridley. Also hopefully Ridley and Dark Samus wouldn't murder me and everyone else in our sleep. I'm sure Mewtwo and R.O.B. could stop that from happening. Maybe Joker and Snake if they had some people watching cameras. I can finally see if Fox has robotic legs or not. Not sure how Wolf would interact with Fox when they aren't being paid to fight each other though. Probably could learn a few things from Robin, Sheik, and Byleth, and they'd probably help keep a bit of order. I dunno anything about Mythra/Pyra, but Pyra seems nice to be around at least. Joker, Dark Pit, Links, Inkling and Sonic seem like they'd be the toughest gamers, so they'd be pretty fun to play against. I'd probably sleep with Kirby and Yoshi since Kirby always seems to be sleeping, and Yoshi shown to be sleeping in Subspace. They probably know where and how to sleep well.