- Buy a Buzzard as soon as you can
- Take advantage of 2x bonus on weekly activities, do heists if you have three other friends, complete San Andreas Flight School, stuff like that
- Once you have nearly 2,5 millions buy the cheapest office (1 mil) and the cheapest vehicle warehouse (1,5 mil), which is also in a strategic position when it comes to steal cars
- Sell ONLY high-end cars, keep the low and mid-range vehicles in the warehouse; when you'll have 10 low and 10 mid-range cars in the warehouse, you'll only spot high- end cars that you can sell for a net 80k profit
- Selling a vehicle solo has a 20 minutes cool-down time; in the meantime, steal another vehicle and run Headhunter with your Buzzard to earn 20k in just a few minutes.
- Once you have almost 1,5 millions left, buy a bunker (I strongly recommend the Chumash or the Lago Zancudo one, just for the strategic position) and focus on production instead of research
- If you have a lot of money left, buy supplies instead of stealing them and keep on repeating the aforementioned I/E process, so the supplies will turn into weapons ready to be sold while you earn money
- Sell the weapons
- Buy the equipment and staff upgrade as soon as you can; this will let you earn more money faster.
Actually, you can buy the bunker first and then focus on I/E like I did. It depends on how you want to earn money.
Bunker is passive, meaning you can earn money while doing other things.
I/E is active, meaning you have to steal and sell cars to earn money.
You decide. Eather way, combining these two businesses will allow you to earn several hundred thousand $ in just a couple of hour of playing.
Gunrunning (if you sell with full public lobby is an extra 50-60k profit)
I once gained an extra 90k, I think it's not a fix bonus but it's about a percentage (like 1% for each player in the lobby or something like that).