The board or joint board of county commissioners shall have authority to hire expert consultants to provide information and assistance and gather information as required; to issue subpoenas, and compel the attendance and testimony of witnesses, and the production of papers, books and documents; and to cause a stenographic or other record made of the proceedings. The expense shall be a proper charge against the county general fund and, when there are two or more counties involved, the expense shall be prorated to the counties in proportion to area.