The Stock Market in Grand Theft Auto V operates with the same goal as real life stock trading: Buy low and sell high in order to turn a profit. The value of stocks dtocks affected by various things including story progress, in-game purchases and with some stocks, other players. The single most important rule of the GTA 5 Stock Market is this: wait as long as possible to perform Franklin’s Assassination Missionsand invest as heavily as possible with all three characters when you do so. No tricks, no fuss. Just wait. The more money you have to invest, the more money you can make on these dramatic and guaranteed market swings.