I don't really think living together is such a good idea. I mean unless you're gonna act like roommates where... this stuff is mine and that stuff is yours. Financially, I think it gets messy... especially if or when you break up.
If you are considering marriage to the person, you are facing all of that anyway. Ownership of this or that matters little if everything is shared in an amenable fashion. It is only things like large joint purchases that present a problem and really should be avoided or handled very carefully.