Image by jessebucksc via FlickrTax-free transfer of property between spouses (including on death) and exemption from "due-on-sale" clauses.
So what happens if you live with your partner and he or she dies. They've been kind enough to leave you the house you share in their will but there's a mortgage on the property. Do you just get to continue making those mortgage payments and have the house transferred into your name like straight couples?
Not a chance. Your home is now subject to inheritance taxes that you'll have to pay or lose the home. Furthermore, if the mortgage has a "due on sale" clause you'll end up having to pay off that mortgage in one lump sum or lose your home.
Without marriage you are not an equal partner in the real estate affairs of your partner but are rather just a tenant as though you answered an ad in a newspaper.