Sounds like at the end of it all, he'll have a car and you'll be out a lot of money. I don't consider it controlling at all, it's your money. Now if it was his money and you were trying to tell him what to do with it that might be different. Expressing an opinion on what someone else thinks you should do with YOUR money is completely sane.
Sales and commision are just to iffy for anyone.
Hugs,