Dispersed round the map (generally in unusual places) there are packages containing money. Grab them so that you can earn several fast dollars.
Apart from the most important quests, Lester will ask Franklin to perform several assassinations in order to favor one or another company. Pay attention very carefully and invest accordingly.
Invest in the Merryweather Security right after the completion of the video game: their stocks definitely will fall down, permitting you to acquire some of them, after which their own value will definitely raise up just as before.
Steal folks nearby ATMs
Track people close to ATMs. Once they had been near one of them, whip and so steal them, next get away from the police.
Within GTA 5 you will find supermarkets which can be robbed. Target the cashier and so wait till he collects the amount of money. Then simply escape. By trying to rob once more a previously conned shop, take care as the clerk could have purchased a firearm.
Complete the Heists
The first heist of the video game (the jewelry store one) will allow you to cash out a lot of money. The other ones much more. The last one will allow you to cash out about 30 millions dollars.
Rob an armored truck
Armored trucks appear at random on the map, you are able to instantaneously identify them. Shoot the drivers, place an explosive on the backside of the vehicle and then blow it, and then obtain the cash.
Saving is the greatest money making method. And so here's a advice: in a task, check out Ammu-Nation and purchase the upgrades of your weapons. Then simply destroy yourself and then retry the task. Check out Ammu-Nation and you'll start to see the upgrades marked as acquired.