Final answer:
A broker must disclose his proposed agency to the prospective client before entering into a single agency agreement to ensure transparency and prevent conflicts of interest.
Step-by-step explanation:
Before a broker enters into a single agency agreement, he should disclose his proposed agency to the party he is intending to represent, whether that is the buyer or the seller. This disclosure is crucial as it ensures that the client is fully aware of the broker's role and the duties and loyalty the broker owes to them. This disclosure helps prevent conflicts of interest and ensures transparency in the agent-client relationship.