Here's what it is for me, I think. If someone wants a written contract/agreement, you are already starting off from a place of distrust nad no amount of paperis going to remedy that. imo
On the other hand, if having a piece of paper makes you feel better. Start off by finding a location, get the landowners permission and then say, "I have this standard agreement spelling out my rights and rwsponsibilities. Would you like to review it and sign it?" and see where things go from there. You may want to do this in front of a Notary Public.
Can you see how difficult that would be for someone w/ 3700 colonies in 50 some yds who travels to other States as well? Somewhat impractical.