The Question: Are we negotiating? The Answer: always. Stands true here as well. Yes, the contract you have for the original price agreed upon is valid, and enforcable. But, If the buyer seeks to modify the contract with diferent terms that may be desirable for one or both parties involved. The seller can accept or deny the request. if the seller accepts the request, then the original contract must be amended to show the specific changes and signed off on again. If the seller denies the reguest, then the transaction continues foward with the original terms, which both parties are bound by. However, you should always consult your attorney.