Rent back to seller, should I?

[Ayne C.]

Im I. A probate situation and the closing has extended 2 times already.  We are looking to close on the 27th of this month but the seller needs more time to vacate.  I'm considering a rent back. What should I charge for rent?  Market rents plus a %premium?  Or should I not even consider a rent back as a newbie?  

It's an all cash deal with a wholesaler.  I'm afraid they will abandon me and run at closing (of course they would) and leave me with a mess.

Should I encourage postponing closing again?  I'm not heartbroken if she backs out.