For sale buy owner contracts

Just want to get some thoughts if someone has found or may have a contract if I was to owner finance a trailer in my park. They would be buying the trailer only not the land. My biggest concern is that they will have to follow the rules of the park or they could loose there contract on the purchase. I cant have them walk over me just because they are purchasing the trailer. I was told along time ago that most people purchasing the trailer would take better care of it and about 80% of the time buyers won’t finish the contract. I had this trailer with a property management company and I never got a full months rent due to repairs all the time and I really hate renting trailers for the most part.

Thanks for any help or direction.