(a) The commissioner shall establish by executive order such units within the department as he deems proper for its administration and shall designate persons to be directors and assistant directors of such units to exercise such authority as he may delegate to them in writing.

(b) The commissioner shall have the authority to employ as many persons as he deems necessary for the administration of the department and for the discharge of the duties of his office. He shall issue all necessary directions, instructions, orders, and rules applicable to such persons. He shall have authority, as he deems proper, to employ, assign, compensate, and discharge employees of the department within the limitations of the department's appropriation, the requirements of the State Merit System, and the restrictions set forth by law.

(c) All employees of the department shall be compensated upon a fixed salary basis and no person shall be compensated for services to the department on a commission or contingent fee basis.

(d) Neither the commissioner nor any officer or employee of the department shall be given or receive any fee, compensation, loan, gift, or other thing of value in addition to the compensation and expense allowance provided by law for any service or pretended service either rendered or to be rendered as commissioner or as an officer or employee of the department.

(e) The commissioner is authorized to provide for the collection of delinquent taxes, including penalties and interest, by contractors. Any such contractors must be approved by the commissioner. No employee of the department shall be approved as a contractor under this subsection. Such contractors shall be compensated only on a commission or contingent fee basis.