To be brutally honest .. not many at all? You get to pick and choose who your gang members are and what permissions/provileges you'll assign them, you set the tone of the gang based around your personality and behaviour you'll tolerate. You get to control which targets you'll pick for Fuck-Off Battle, Gang raids and participating in the tussle for 2nd map locations to give your gang a bonus in various endeavours, as well as what which upgrades you will build once yur gang safe has enough cash.
That, pretty much, is it.
As for income ... any gang member who participates in a FOB will get a percentage of the winnings, but the boss gets no more than any other member.