Complex sentence: Other key members of the Improvement Club were Raymond McGruder and Joseph Robert Ball, Jr. Prospective members of the club had to go through a probation period, be voted on by the board and then pay a fee.
Split into simpler sentences: Other key members of the Improvement Club were Raymond McGruder, J.R. Ball. To be a member of the club you had to go through a probation period, be voted on by the board and then pay a fee.