So if Gangs who control bases gain a percentage of the sales on shops within that base's zone, How exactly does that work, Like when a player buys something they receive money or what? because Someone bought a gun in our zone and nothing happened lol.  

I believe that is how it works, it usually varies based on the base.

If you were located in Gangster Zone, some shops in that territory give you profit, aka 'hope that someone buys an M4'. The profit varies based on the actual prices that the shops have and the actual base.

I assume it's based on a certain algorithm. I think it'd be cool to have someone thoroughly research this.

My guess is that it's a certain percentage based on how many products are bought.
For example, Rob bought an M4, then Carly, then Albert. When Albert got his M4, the base made profit. I guess the system just counts how many people buy products in the shop and gives out whenever a certain amount is given.

This is just a guess though. I'm likely wrong.

If you were located in a base that has no profit (I believe it's only Neo Zone, Tachi can make profit, just never does), then nothing happens.