The purpose of a buyer's final walk-through of a property just prior to close is to verify that the seller has maintained the property in the same condition as when the buyer went into contract. It's also to make sure that the seller has completed any negotiated repairs. 

Generally a walk through is scheduled within seven days before the closing.  A walk-through is important-- you don't want to close on your new home then move in to find scratched hardwood floors from when the Seller moved out, or trash left in the garage. Other problems I've seen come up during walk throughs are doggie-doo in back yards, removal of attached appliances (like microwaves) or even the removal of walls and doors (!).

A walk-through cannot serve as recourse so you can get out of the contract. It's sole purpose is to verify property condition.  However, If the property has not been maintained, or the seller hasn't completed the required repairs (or not done them properly), you and your agent should try to get the seller to make the corrections prior to close of escrow (COE).  

If repairs cannot be completed on time, you can:                        

A.  Extend the close of escrow to allow seller time to do the work.              

B. Negotiate a credit from seller for buyer to complete the work after close of escrow. The amount of the credit should be enough for you to complete the repairs or maintenance.              

C. Have seller and buyer agree to a hold-back of funds for seller to complete the work after close of escrow. We try to avoid this last option-- things can get very sticky when the seller or the seller's contractors hae to come out to work on your new home. We've often had instances where the seller never completes the work, delays on doing the work, or our client and the seller don't agree on how the work should be done.    

If issues arise during the walk-through that can't be resolved, you may cancel the contract. But this last resort should only be taken with the advice of an attorney who can  confirm that the seller actually is in breach of the contract because of seller's actions or failure to act.