After a joint industrial farm and workhouse has been erected and equipped and is ready for occupancy, the president judges of the courts of common pleas of the counties joining in the construction of the joint industrial farm and workhouse shall appoint an advisory board to consist of three persons from each of the counties. The president judge of each of the counties shall appoint one member of the board to serve for one year, one to serve for two years and one to serve for three years or until their successors are appointed and qualified. All appointments at the expiration of any term shall be for a term of three years.