First, you must own a vehicle in Career mode. Sell it and exit the game.
Then, open the "metal.ini" file in the System folder of the game directory
(default is C:\Program Files\Terminal Reality\4x4 Evo2\system). You can 
use Notepad to open the file. Scroll to the bottom of the text and within
the final 20 lines or so, you will see the lines "careerTruckCount=0" and
"curTruckType=0". Change the "0" to a "1" in each line and save the file.
Now restart the game and go to the Garage in Career mode. You will have 
the vehicle back AND the money you sold it for before! Do this whole 
process as often as you want and watch the cash add up!