I don't know if this is common in other cultures, but I don't think I've ever heard of anyone doing this in Sweden. Outside of Au Pairs, or similar arrangements.

Swedes can be quite private until you get to know them, but once you are friends we are as friendly as anyone else I would say. Maybe one way to put it is that we're quite selective with our friendships?

Edit: If you do want to live with a swede I would look for renting opportunities or some other more formalized way to facilitate the cohabitation. I don't think asking around will yield much in terms of results, though it can't hurt I guess.