Crash the Parking Meters
Drive along the side of any street in the Vice City downtown area, and you'll notice tons of parking meters. Run one over to send its contents pouring into the streets. Then get out and pick up all the cash lying around. Repeat this trick for some really quick cash.
Model Citizen
Head to the mall and follow a policeman. Eventually, he'll start chasing someone. Beat the cop to the punch (literally) and start hitting the guy he was chasing with your fists. You get $50 for each punch. Make sure you're not wearing the brass knuckles, and be careful not to hit the cop. If you do, he'll try to arrest you instead.
Rob the Bank and Local Stores
Complete "The Job" mission. Afterward, you can return to El Banco Corrupto Grande by walking right into the building. Rush upstairs into the manager's office and the elevator room and grab the cash you find. You'll get the four stars wanted level; to escape, rush over to the local pay-and-spray right up the street to your left.
Any store can be robbed as well by pointing a gun at the clerk and aiming at him until he drops three cash pickups. Make sure you have an escape plan---the clerk pulls the alarm, causing the cops to chase after you.