The board of supervisors in any county having more than 900,000 population may, in addition to any other revolving fund, establish a revolving fund to be used by the purchasing agent of the county in paying for services, materials and articles of personal property which he is authorized by law to purchase and which constitute a legal charge against the county. When any materials or articles of personal property designed for building construction work are purchased from the revolving fund provided for in this section, such materials or articles of personal property shall be used only in connection with repairs to existing structures. Such revolving fund may be fixed in an amount sufficient to enable the purchasing agent to meet the cost of the services, materials and articles of personal property purchased by him. In all other respects, the provisions of this article shall apply to the revolving fund provided for in this section.