After the «Fame or Shame» mission, Franklin will be able to get more tasks from Lester. They include stock market missions and assasinations. If you want to quickly make 100000$ dollars in GTA 5, you should try completing Lester’s missions. The main thing here is to not complete any random events while you’re at it. Make sure to finish missions from strangers before you start helping Lester.
However, you can play the ones that are not related to stock market, like «Hitch Lifts 1» or «Bike Thief City 1». You should also wait until you receive the payment for the assassination before you start another one. Don’t buy any expensive cars or property before you get paid. Purchasing vehicles, garages, helicopter pads and hangars won’t help you with missions anyway.
After you’ve completed all Lester missions, you can get back to finishing random events as they won’t affect your progress anymore.
