My father in-law owns an investment property that he has allowed some less than desirable relatives to occupy the property rent and agreement free for ten years. The total cost of maintaining the property has been absorbed by my father in-law. Now the time has come to sell the property and I foresee a battle in removing the current occupants. The occupants have no means to purchase the real estate or provide rent. The property is unsellable while these people continue to squat. How can the occupants be legally and quickly removed to expedite the sale?

Even though they do not have a lease agreement or pay any rent your father-in-law needs to give them a written notice that their tenancy has been terminated and they must move out within x number of days. The time depends on the laws in that state. In most states 30 days is sufficient but some states (like California) require 60 days. If they haven't moved out within that time then your father-in-law needs to file a lawsuit for eviction.