Residents most of the time should not buy homes, especially if they're not in a stable, professional and personal situation. Living with your girlfriend is generally not a stable personal situation. Make it very clear from the beginning what's going to happen if you break up because this is a business transaction. You don't want to buy a house with somebody that you're not married to. It just gets really ugly. More better for one of you to buy the house and the other one to rent from you or to live there free or whatever.