There are many different ways of earning money in GTA Online, But what I would recommend doing is Cayo Perico Heist, it pays around $1,300,000 every time you do it solo, besides that I would recommend Vehicle Cargo, the payouts arent the highest but it adds up eventually. On the side you can also buy supplies for your MC businesses and sell those from time to time. I would go into more details but there are a lot of good guides out there on youtube that can do that job for me, I hope this helped and thanks for commenting :)
How do you get all that money? There’s no way you can get a couple billion in just gameplay but that many Shark Cards are roughly 8 thousand dollars and if you’re in school then that wouldn’t be very affordable? I’m just curious
