The Cliff Notes answer to your question is simply who ever wants possession of the property you occupy. The old owner has no rights and other than your security deposit, has no obligations to you. The purchaser may or may not owe relocation assistance based upon a variety of factors that are far to convoluted to be discussed in this forum. If the entity who purchased the property at foreclosure sells the property, its the new owner that would owe the relocation assistance, if it applies.
A proper response would require a thorough investigation into the history and background of this relationship. The information provided above is just that, information, to be used as you see fit.