Wwoofing agreements?

I’ve had several folks come and go over the years helping around my property. Typically some form of work trade. Usually the experiences are mutually beneficial and pleasant and when it’s time for a change, we’ve all been able to move on and respect each other.
Of course, there are exceptions. In fact, I recently had to ask a fellow to leave because he found that hanging out in his cabin and self medicating was of greater importance to his own needs than meeting our agreed contributions to the property. While he did leave, eventually, he also left a fair amount of “stuff” behind. Stuff that I am now responsible for disposing of. Bummer. As if there aren’t other things my time and energies could be better spent on.
While this is an exception to my experiences, I know it’s not a lone one and each time I open my space up to others, I put myself at risk. Sure, cleaning up someone else’s leftovers is a relatively small risk, but I also know there are greater risks out there and would like to protect myself from those risks as well as have a clearly articulated set of expectations and boundaries. Does anyone have a contract that they use for farm-stay help? Whether work trade, Wwoofer’s, interns, or volunteers?
Thanks for your time.

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