Which action is not permissible by a salesperson when a customer expresses interest in purchasing a home without entering into an agency relationship?

When a customer expresses interest in purchasing a home without entering into an agency relationship, disclosing a previous offer from another buyer is not permissible. This action involves sharing confidential information that relates to the seller's negotiation strategy and puts the seller at a disadvantage.

In real estate, confidentiality is paramount, and the responsibility to maintain such confidentiality extends to the salesperson when there is no established agency relationship. The salesperson is not legally or ethically allowed to disclose sensitive information that could harm the seller's position in negotiations.

On the other hand, explaining the concept of dual agency, providing information on properties for sale, and giving details on mortgage interest rates are permissible actions, as these do not breach any confidentiality agreements and can assist the customer in the purchasing process without compromising any parties involved.