In California, the residential real estate purchase contract allows the buyer the opportunity of a Final Walk-Through and Verification of Property Condition at a mutually agreeable time approximately five days prior to escrow closing. 

If the seller agreed to make any repairs, the buyer has the opportunity to verify that the repairs were acceptably completed.  It is also wise for the buyer to request copies of any paid invoices. 

The purpose:  verify that the property is in substantially the same condition as on the date the buyer contracted to purchase.  The walk through is not:  an opportunity for the buyer to renegotiate.  The seller is not:  required to attend but sometimes graciously extends this courtesy.