The County Board shall provide suitable office quarters for the use of the Public Defender, and shall pay out of the county treasury for necessary office, travel and other expenses incurred in the defense of cases. In counties of less than 500,000 population, such payment shall be made after the circuit court of the county approves such expenses as being necessary and proper. In cases where 2 or more adjoining counties have joined to form a common office of Public Defender, the expenses incurred under this Section shall be paid as provided for in a joint resolution of the various county boards involved.