story mode

how can i get cash in story mode

-heist
-assassination mission
-Stock exchange (LCN or BAWSAQ)
-use trainer

When you do the assination missions. Invest in whoever their competitor is before killing them and there stock price will fly up. If you listen to what lester says when your doing the missions you might not have to look up the exact missions and companies to invest in.

There are a lot of trainers you can use, I forget their names, but there are a lot of good ones.