Not easy. Usually all you have is a bill of sale. One thing to look for is the model/serial number identification. If you can find that and it's intact, you may be good to go. Older tractors probably aren't financed.....in the sizes that I see respondents to this site advertise to possess. Newer you might have a question as to wether or not a note is pending. Not a lawyer so I don't know the rights of the lending institution in terms of to what length they are legally allowed to repossess their property if it's been sold. About all you have is the word of the seller....aka know your seller! I do know that stolen property can be confiscated by legal authority!