Answer: the prevailing party all reasonable costs
Explanation: The prevailing party is the winning party in a lawsuit. Most contracts dealing with buying and selling of real estate provides that the prevailing party shall be entitled to claim certain costs and expenses such as attorney's fees if legal action has to be taken for the agreement entered upon to be upheld.
The only times there are no prevailing parties are when a complaint is voluntarily dismissed or when the case is settled before trial begins, and sometimes when trial has already begun but before a final judgement is entered.
This clause in the agreement usually deters both parties from bringing frivolous lawsuits.