Maybe have it in a way that you have these land plots laid around in various locations around the map, ranging in different yet expensive price points to separate the smaller and the larger gangs. The plots will not be purchasable but rent able making it so a gang has to keep paying for the plot or else they will lose it. After a plot is obtained a gang can increasingly upgrade their base which will cost them even more money to buy different shops,garages and maybe fortifications. That way a more established gang that needs a fitting base for it's operations will be distinguished from a smaller gang that only have minimal load out needs but can afford to buy a base to avoid taking the risk at rebel.