The Cayo Perico Heist is a good start, the payout has been lowered several times since then but is still the best way to make money and you can solo the heist. If you have a friend with you the Diamond Casino heist is another option. The Doomsday Heist Act II and Act III have good payouts, Act II is easy where as Act III can be difficult for players that are inexperienced.
The Auto Shop business has contract heists which are smaller heists that have a decent payout ranging from $170,000 - $300,000. The Acid Lab is a good starter business it spawns nearby your location when called upon, sell missions are fast. The value of the product when sold with the equipment upgrade in a private lobby is $335,000 or $500,000 in a full public lobby.
The AP Pistol is accurate and has a high fire rate which makes it a good weapon to have while driving. The Assault Shotgun with the drum magazine is good when you're taking on multiple enemies at short range. The Mk II weapons are some of the best guns in the game, there is a weapons workshop you can use for free at The Freakshop which is unlocked after First Dose 1 - Welcome to the Troupe mission. The Service Rifle and the Battle Rifle have the same fire rate but the BR has more power where as the SR has a bigger magazine. They're both expensive but good alternatives to the Mk II rifles.
