Seller occupying for 2 months

[Dilini Peiris]

We just purchased a property through a whole seller, not closed yet, but seller has given us permission to start on rehab, but is wanting to occupy the property for 2 months. What paperwork do I need to set up to ensure they will leave in 2 months and should I get specifics of what rehab we are allowed to do while he is living there? And if so how and what kind of agreement do we need ?