Hey! I'm really late to this one! But it should come as no surprise to anyone here that I am way behind the times and have only recently bought a Next Gen console (PS4) and am now enjoying a 2nd run-through of the GTA 5 campaign (it's my 1st go with the super awesome Enhanced Version and 70-inch TV though). I just finished a focused speed run through the main campaign and have been selecting Lester's Assassination missions, which has a very lucrative glitch that I thought I'd point out:
It's fairly common knowledge that one should save these missions until after the completion of the main campaign so as to maximize investment return, and I had just completed the 2nd Mission (The Multi-Juror Assassination) which should've netted me about 80% initial return on Debonaire, and a subsequent 300% return on Redwood after a few days (based on +/- $30,000,000 principal). I then immediately loaded the end of mission autosave because I thought I had messed up, and when I checked Franklin's portfolio it had increased by over $900,000,000. Michael's and Trevor's too. Thus, after only two assassination missions, all of my guys had roughly $1.2 Billion. This is apparently an autosave fault within the LCN market and is time sensitive; you must sell all of your shares within the first few minutes to take advantage, because the market corrects itself after a couple of in-game hours. The Gold Coast Construction shares affected in the last mission are also traded on the LCN, and I'm going to try duplicating this windfall there too once I have the time to play again.
Update: Yup. It works. Sort of. $2,100,000,000.00 plus seems to be the in-game cap. Based on the return percentage, I should've netted closer to $4,000,000,000.00, but whatever.