Final answer:
A written agreement is required to make an exclusive listing agreement valid.
Step-by-step explanation:
In order to make an exclusive listing agreement valid, the requirement is a written agreement.
A written agreement is essential because it clearly outlines the terms and conditions of the agreement and provides a record of the agreement between the parties involved. It helps to avoid misunderstandings and disputes that may arise in the future.
Verbal, handshake, or email agreements are not sufficient and may not hold up in a court of law if any disputes occur.