The seller and buyer should be truthful in their transaction. They should not conceal any defects with regard to the price or sold item, as defects decrease the value of the sold item. Moreover, it is a form of deception. The Prophet (peace be upon him) said:
"He who deceives us is not of us (is not my follower).''
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.