Not really. Anything that gives you an advantage in combat is gated by level. As for races, I could see it slightly, but custom vehicles are very rarely allowed, making that a moot point. Money is easy as hell to make in GTA. I haven't spent a cent on the money in game and yet I have 5 properties, every supercar maxed, several air vehicles (including the Besra jet and Swift helicopter), a tank, and several other cars maxed.