The state fire marshal shall appoint one assistant director and such other investigators and employees as the needs of the office require within the limits of the appropriation made for such purpose. No person shall be appointed as an investigator or other employee who has been convicted of a felony or other crime involving moral turpitude. Any person appointed as an investigator shall be of good character, shall be a citizen of the United States, shall be a graduate of an accredited four-year high school or, in lieu thereof, shall have obtained a certificate of equivalency from the state department of elementary and secondary education, and shall be a resident of Missouri at the time of appointment. An investigator or employee shall not hold any other commission or office, elective or appointive, or accept any other employment that would pose a conflict of interest while he or she is an investigator or employee. An investigator or employee shall not accept any compensation, reward, or gift other than his or her regular salary and expenses for the performance of his or her official duties.