Start the game with these paramaters:

 -cheater -infinite -nocar -invince

In game: press Alt-Ctrl-F7 before anyone hits you or you hit them 
and you will be invincible, no cars on the road, and infinite weapons.

Need more money?
Hex edit SAVEx.GAM   (x being game number)

Sector 0, offset 407-408: change to 0F 27