California Code, Government Code - GOV § 31000

The board of supervisors may contract for special services on behalf of the following public entities: the county, any county officer or department, or any district or court in the county. Such contracts shall be with persons specially trained, experienced, expert and competent to perform the special services. The special services shall consist of services, advice, education or training for such public entities or the employees thereof. The special services shall be in financial, economic, accounting (including the preparation and issuance of payroll checks or warrants), engineering, legal, medical, therapeutic, administrative, architectural, airport or building security matters, laundry services or linen services. They may include maintenance or custodial matters if the board finds that the site is remote from available county employee resources and that the county's economic interests are served by such a contract rather than by paying additional travel and subsistence expenses to existing county employees. The board may pay from any available funds such compensation as it deems proper for these special services. The board of supervisors may, by ordinance, direct the purchasing agent to enter into contracts authorized by this section within the monetary limit specified in Section 25502.5 of the Government Code.