The executive director may employ a staff in accordance with the State budget. Except as otherwise provided by law, the staff is in the skilled service or professional service, with the exception of special appointments, in the State Personnel Management System. The executive director shall employ an investigative staff in accordance with the State budget. The executive director may contract with an expert, subject to the State budget, if the services of an expert are required in a particular case. Investigative staff and contractual experts shall investigate only complaints about home improvement.