Basically, you need to leave Lester's assassination missions until the very end of your playthrough, giving you the largest sum of GTA$ to be invested in stocks and in turn producing the largest payout. If you play your cards right, all three protagonists will be walking around with millions. However, the stock market is also the solution to the money problems you might have in story mode. It would skew the balance and negatively impact the game experience of players who don't want to resort to using cheats. Players who use cheats to add large sums of money would be able to affect stock prices for non-cheating players as well, and Rockstar can't have that. However, we have an excellent resource to help you earn millions of $GTA from the stock market regardless. If players had access to unlimited cash, it would make this feature meaningless. Each player affects the market and all other players will see stock prices rise and fall accordingly. The simulated stock market in GTA 5 is connected across all instances of the game in order to make it feel a little bit more like a real stock market.
The reasoning behind there being no unlimited money cheat in GTA 5 story mode is simple.
