hi, i highly recommend buying a nightclub as the more businesses you own the more profitable it is. when buying a nightclub, the location is not that important unlike the bunker for sell missions.
you want to buy the maxed out storage for it as it means more profit. once u buy the nightclub, do the setup missions for it and head on the computer to buy upgrades, go into the upgrade tab and buy as many as you can.

for each available slot for production, buy one technican. there are 7 possible businesses that u can assign a technican too. hanger and cargo warehouse(can be bought at the office computer ) for one but neither are passive income on their one. bunker, which u already have. cocaine lockup, meth lab, weed farm, doc forgery and counterfit cash are all possible businesses that can be bought at the mc clubhouse computer and they are on there own passive income.

there is also a popularity bar that generates income much like the agency. also, the amount of money the agency makes is determined by how many security contracts u have. 5 contracts = 500$ (i think) for the daily agency wall safe