Have had this exact same problem so I asked the attorney for the state park owner’s association how to handle it. She said many park owners are now charging a “move out” deposit that is separate from the security deposit. We can charge a security deposit in OH equal to 1 month of rent. We can also charge a move out deposit without any limit. She suggested $1,000 as this is what many parks are charging but that is too much for my area. I charge $500 and have had no trouble collecting it.
The deposit ensures that in the case of a home moving out, I have some funds available to cover damages to the lot. If someone wants to sell their home, they don’t get their money back until I have approved the new buyer(s) and they then put up the required deposit.
Here’s the problem: This only works when you control the new people moving in. It’s pretty much impossible to collect this from existing residents certainly from a practical standpoint and possibly from a legal one as well. It sounds like it is existing residents that are moving out and letting the scum in. In that case, Brad’s suggestion in probably the only realistic solution.