Don't buy a home with a 'partner' (other than your spouse)
There are, frankly, too many things that can go wrong. (Just a couple of the scores of examples: what happens if the partner wants to sell and you dont? What happens if the partner stops paying?) If you insist on buying with a partner, then sit down beforehand, and think of all the things that could go wrong, and how you would handle them if they did. If you can agree... put this in writing. If you can't agree, then don't buy the house together... and this includes unmarried couples buying a home who intend to get married.