I would agree to keep the lawyers out of it if at all possible. You have already said that you can't go 50-50 on the boat, so let's say it's 70-30. Are you going to split upgrades and equipment costs 70-30 as well? What a pain. And what if you break up and nobody wants to sell the boat, but neither can afford to buy the other out, even if you could compute a fair value. Headaches! I would let him buy the boat, but stress that he must also pay for maintenance and upgrades. Half the slip rent & varnishing could be considered your "rent" for otherwise living for free. Put your cash into AT & T stock with a 6% dividend, and if you break up, I'm sure you'll be better off.