The Commissioner may upon his own motion and shall upon a written complaint signed by a citizen of this state and filed with the Commissioner inquire into any alleged illegal or improper conduct of any licensee or inquire into the question of whether a licensee is untrustworthy or not competent or not qualified to act as a licensee under this chapter. No finding or decision adverse to any person in regard to whom the inquiry is conducted shall be made by the Commissioner until after notice and hearing as provided in Chapter 2 of this title.