Within the movies and certain information from various houses. Yes, I heard it was possible, but not with an apartment. I think it is going to possible upon release on "plot" houses or guild halls.
Yes you can room with as many people as you want. And rent as big of a place as you want. Although there is nothing to do in your place but make it into a very decorated bazaar stand. The selling is done out of the housing areas through a vendor in the main part of town. The bigger the place the more people can set up shop there. Hope this makes since. and hope it helps
Your home (or room) is also were you keep your pets. The way it would work is one person would own the house (room) and set the other(s) as trustees. There are some expensive homes and some require Status points (earned through guild related quest) as upkeep. It has also been stated by devs that expensive or rare funiture will decrease upkeep cost. A trustee should have most of the same control over a home as the owner.