Enter career mode, buy a car, then go to the circuit selection screen. Choose any circuit and enter the first race. When you get into the first race, press [Esc] to pause game play. Click on "Quit", then "Main Menu". The game will ask if you want to forfeit the race. Answer "Yes and you will return to the main menu. Do this for the three races in the circuit, and you will gain $100 at the end. This is a quick and easy way to gain money.
When you complete the European tour, go to the High Stakes tour and choose the Knock-Out race. You will have to pay $3,500 to enter the race. When you start the actual race, press [Esc] and quit to the main menu. The game will say that you lost the race and give you $4,000 as a reward for coming in last.