Spent a lot of time on the market these past few days, and it's a complete and utter farce. Smoke and mirrors. Entirely randomly generated stock movement. Forget those "Bomb competitor 'A' and profit with competitor 'B' " how-to videos and strategy guides put up by "knowledgeable and experienced" gamers. They're all bullshit.
For example, I invested in TacoBomb and spent two in-game days destroying Cluckin' Bell trucks and evading Wanted Levels in Paleto Bay. After 25 Sticky Bombs, TacoBomb's stock was worth less than what I paid.
Somehow, a long post I just put up is gone.
I talked my wife into buying a bunch of TacoBomb stock with all three characters and she blew up 7 Cluckin' Bell trucks. The stock has done nothing but drop since and she bought it fairly low ($243 or $244/share). I'm sorry I posted the link recommending it.
She's 30% in to the story and Franklin still has only $30k. Stocks aren't cutting it, she can't buy a business/property and she can't rob stores or sell cars like she sees me do online.
How the heck do you make money in story mode?!?!?!?
Edit: We'll give EMU a shot.
Don't feel bed for posting the link. You were trying to help, and had no way of knowing that the info was flawed. The people who put that info up were trying to help too, but the thing about the internet is that when bad info gets sent out, it stays forever.
Using EMU, or any other stock, becomes a real grind. You have to keep checking the markets every few minutes over the space of an in-game week or two, and after you sell off you still have to keep checking for the stock to drop, buy in again and repeat the cycle. Not much fun.
There's a quicker exploit you can use to pick up some easy cash: Every underwater wreck site has a respawning suitcase full of cash. The biggest one ($25K) is located not too far from shore, roughly SE from the Pacific Bluffs Country Club. It's also in shallow water, so you won't need scuba gear to get it, and there's almost 0% chance of encountering sharks at shallow depths. The case sits on top of some kind of abandoned underwater facility, next to a large open circular hatch. When you've nabbed the case, swim to the surface, pull out your phone and do a "Quick Save". After the save is done, reload that save. When the game reloads, the money case (and the underwater weapon pick-ups) will have respawned. Pick up the case again, surface, save and repeat as often as you like. 10 cycles gives you a quarter of a million, and takes a fraction of the time of waiting for the stock market to do anything useful.