1. Enable passive session. $100 is a lot cheaper than $2000 hospital bills.
2. Dive into missions. Freeroam sucks if you're trying to level/make money. Accept missions the NPCs give you by cell phone. They pay better and give more RP for completing than robbing liquor stores or some of the random missions scattered around the map.
3. Different missions give different benefits besides RP/money. For example, you can't add turbos to your personal car until you've completed X number of races with cars of that type. So plan accordingly.
4. Things get pretty good around level 15. Do the survival mission in the north central boonies and you can net $20k + 3.5-4k RP every time you do it. 1-4 people but 4 is preferable. Hole up in the barn with shotguns - max out your shotgun ammo prior to the mission. Don't worry about other guns, you'll pick up plenty between waves that you can use on the choppers in later waves. Complete 10 waves for the $20k. Takes roughly 10 min (not sure, didn't really time, but it seemed relatively quick) to do 10 waves with a good crew.
5. Every time you log in, steal a Felon GT or Range Rover thingy and sell it to the nearest spray shop for a cool $9500-ish. You can do this about once an hour. I leave my personal car in my garage (Gauntlet). Steal/sell another one after you've done missions for a while.
