Head on over to Bringley Hill, enter one of the stores and start a robbery. Don't kill anyone, just punch them a bit, try not to allow them to scream for help. Collect $1,000, and take your loot to the robbery car. If you have three stars or more, go to the Outlaws crib. Enter it, then go out and you'll have no stars.
Cheap Shots and More Easy Money:
You can quickly get some more cash by busting open pay phones and parking meters... You don't get too much, but if you can do a lot of them you'll build up a healthly load of cash.
When your rage meter is full, press L + R2 and you should be faster and stronger.