Which duty requires agents to act in the best interests of their clients even if it costs them personally?

The duty that requires agents to act in the best interests of their clients, even at a personal cost, is known as the duty of loyalty. This fundamental obligation ensures that agents prioritize their clients' needs and interests above their own, fostering a relationship built on trust and fiduciary responsibility. This duty is crucial in real estate transactions, as it helps to guarantee that agents are fully committed to advocating for their clients, ensuring they receive the best possible outcomes.

While other duties such as accounting, skill, and disclosure are also important components of an agent's responsibilities, they do not specifically encapsulate the notion of prioritizing the client's interests above those of the agent. The duty of loyalty is distinct in its focus on placing the client’s needs first, thus reinforcing the importance of ethical conduct and integrity within the professional relationship.