OK, thanks. Forgot to mention: Does it matter if new owner has taken possession or or moved in yet?
No! If escrow closed and the new owner owns it, he/she can do whatever they want - move in, not move in, etc. You can only force the recission of the contract if there was fraud, etc. by the new owner. Imagine if you bought a house or a car or anything else and the person who sold it to you came back later and said they changed their mind. How would you feel? The former owner can ask the new owner if he/she will sell it back, but the new owner has no duto to do so.