How to put a lean on a property?

HI there: my father is a retired minister. His former conference purchased a piece of land for the purpose of providing a lot or two for retired minister to bring in their movil homes (this is the only retirement plan provided by the conference). My father has lived and worked on this property for 12+ years. Several years ago the former conference merged with another conference but the property kept its mission. However, lately we have heard the new conference wants to sell the property. I am afraid my parents will be displaced from there home. Like I said before, my father worked in the property as a grounds keeper for more than 8 years without pay. If the conference is selling the property and making a profit. Doesn't my father have the right to claim something? if so, we need to act quickly. Please advise.