A real estate broker shall not commingle the money or other property of his principal with his own and shall at all times maintain a separate, special bank account to be used exclusively for the deposit of said monies and which deposit shall be made within three business days. Until such time as the money is deposited into a separate, special bank account, it shall be safeguarded in a secure location so as to prevent loss or misappropriation. Said monies shall not be placed in any depository, fund or investment other than a federally insured bank account. Accrued interest, if any, shall not be retained by, or for the benefit of, the broker except to the extent that it is applied to, and deducted from, earned commission, with the consent of all parties.