Final answer:
A broker must give a prospective buyer a copy of the initial agency disclosure pamphlet before the buyer signs any contracts.
Step-by-step explanation:
According to the question, a broker must give a prospective buyer a copy of the initial agency disclosure pamphlet. This should be done before the buyer signs any contracts or makes a purchase offer, ensuring that the buyer is aware of the agency relationship and any potential conflicts of interest. Therefore, the correct option is B. Before the buyer signs any contracts.