The district court may authorize the executor or administrator of any estate to enter into a written contract with any bona fide agent to secure a purchaser for any real or personal property of the estate, which contract shall provide for the payment to such agent, out of the proceeds of a sale to any purchaser secured by him, of a commission, the amount of which must be fixed and allowed by the court upon confirmation of the sale; and when said sale is confirmed to such purchaser, such contract shall be binding and valid as against the estate for the amount so allowed by the court. By the execution of any such contract no personal liability shall attach to the executor or administrator, and no liability of any kind shall be incurred by the estate unless an actual sale is made and confirmed by the court.