I've recently finished all 69 missions in the main campaign, and everyone has about $26 million in their bank accounts, but that isn't nearly enough to buy all the different properties in the game (the golf course is $150,000,000 by itself!).
Apparently it's possible to become a billionaire, but most people do it through judicious use of Lester's assassination missions. Unfortunately a lot of people will be like me; finishing the game before looking at any tips, tricks or guides. So how can I now take each character's final money and turn it into more?
I've read theories about manipulating the LCN exchange (the market tied to your single player game) by damaging rival companies so their competitor's stock rises (or the target's stock falls).
For example, CoolBeans vs BeanMachine or Burgershot vs Up-An-Atom. The theory goes that if you blow up a bunch of FlyUS airplanes, AirEmu's stock will rise (or at least, FlyUS's stock will plummet). But as far as I can tell, these are only rumours and nobody has actually been able to make any money doing it.
There's also obviously the BAWSAQ, which are, in theory, tied to fluctuations in both GTAV and GTA Online across everyone's game.
So how can I turn my characters in GTAV (not GTA Online) into billionaires?
Note:The "invest in Debonaire" answer below does NOT WORK.
Best Answer
I haven't had much luck trying to destroy assets to affect stock prices either. But here's what's been working for me so far. It's not a guaranteed quick-billion but over time you'll get there.
Invest in Debonaire!
The stock price for Debonaire consistently fluctuates between around 4.8 and 7.4 (at least from what I've seen in my ~60 hours of story mode gameplay). Since the price is so low, that tiny change is actually a significant percentage. If you invest everything in the stock when you see it anywhere below 6 or so and then sell it back any time it goes over 7, you're making a decent percentage (up to 54%!) back on your investment at a relatively frequent interval.
If you are actually trying to reach $1,000,000,000 then this method is going to take a long time. There's probably something better out there. But at least it's something reliable to do until someone finds that better thing.
As for precisely how long, given your starting balance of 26 million and assuming an average ROI of 10% (YMMV) and ZERO extra spending, you'll have to invest and sell everything 39 times to reach a billion dollars. But only 19 times to afford the golf course.