Add Money 
Enter MEGASAXON at the New Career screen to get 1,000,000.
 

Hex cheat
Begin a new career and save the game. Write down amount of money you have, 
convert it to hex string, break it onto two parts and switch their positions 
(example: 1000 > 03 E8 > E8 03). Use any hex editor to open the savegame file 
(it's in the "Leadfoot\Data\Saved Game" folder). Find your string and replace it 
with EA 60 for example to to get 60,000. Now load your savegame....