No pain for unlimited money:
Press $ and shift and hold them and watch your money go up rapidly. But to make sure there's no pain in getting millions of money make sure you do it at the start of the game when you have no enclosures otherwise the fences will break and your animals will escape and then you'll have to buy new animals and new fences which will drain away your new money.
Zoo Tycoon: Dinosaur Digs PC cheats 
