No Lease

[William R.]

A friend explained a situation to me the other day,that I didn't know what advice to give.

They have a relative that they have allowed to live in a property rent free for several years with no lease.  They cut the grass and take care of a few things in exchange for rent. As you'd expect... now things are not going so well and they'd like them to move.  

My advice was that first and foremost they need to sign a lease.  Can they force them to sign a lease?