Retaining Resident Owned Homes after a Flood

We re trying to recover from a major flood in the Midwest (Southern IL) which caused the evacuation of the entire park for 4 weeks. The majority of the homes are park owned and we lost a lot of tenants. Now a few of the resident owned are saying that they are thinking about selling. These people have been here since we bough the park and they had no background checks. Since we purchased the park we have done a background check on all new people for resident or park owned units. Is there a good way to alert them to the fact that whoever buys their trailer will need a background check to be able to live in the park without bringing up the idea of selling to any resident who wasn’t thinking of it?