That really depends on terms & conditions of the offer that was accepted and agreed to by both parties. The biggest factors include: timeline to close, home inspections and lender/financing contingency time frames.
It also may be effected by outcomes of the inspections (as in what has to be repaired and how quickly this can be completed and reinspected for approval). You can imagine if a new roof needs to be put on in order to satisfy the buyer, insurance company and/or lender, then the closing date may have to be pushed back or out considerably.
At some point too you are at the mercy of the lender and their staff to underwrite, approve and process the necessary paperwork. I think it's safe to say that if all goes well, both parties are communicating well and there are no surprises, that you should be able to get through it all within 30 - 60 days or less.