If a licensee knows or should have known that he, any member of his family, his firm, any member of his firm, or any entity in which he has an ownership interest is acquiring or attempting to acquire or is selling or leasing real property through purchase, sale, or lease and the licensee is a party to the transaction, the licensee must disclose in writing that he is a licensee and that he, any member of his family, his firm, any member of his firm, or any entity in which he has an ownership interest has or will have an ownership interest to the other parties to the transaction. This disclosure shall be made to the purchaser, seller, lessor, or lessee upon having substantive discussions about specific real property.