Which of the following is NOT a method of terminating an agency?

In the context of agency relationships in real estate, there are several recognized methods for terminating an agency. The correct answer highlights that broker costs do not serve as a method for ending an agency relationship.

Expiration date, revocation by the principal, and mutual agreement are all established ways to conclude an agency. When an agency agreement reaches its specified expiration date, the relationship automatically ends without the need for further action. Similarly, a principal has the authority to revoke the agency agreement at any time, although they may face legal repercussions or obligations for any contractual obligations. Additionally, both parties can mutually agree to terminate the agency, indicating that they are in agreement about ending the relationship.

In contrast, broker costs relate to financial expenses incurred by brokers during the agency's operation and do not impact the legal standing or the mechanisms of how an agency is formally terminated. Thus, this is why broker costs are not recognized as a method of terminating an agency.