Just check out some guides on how to do the heist properly. Once you’ve got that you can easily clear 1m an hour solo. Don’t buy the other sub upgrades until you have more money, they’re not necessary. Your first goal should be to save up the 2.2m you need to buy the Kosatka submarine, then get the Sparrow helicopter with missile upgrades as soon as you can afford it.
Nothing earns money faster than doing the Cayo Perico Heist.
