Big Spender

Big Spender is an achievement/trophy in Dead Rising 2. It is unlocked for spending 6 million dollars ingame.

Guide
Gather your money first, either by Terror is Reality events or by gambling (the giant slot machine is the best for gambling) and then save. Buy the SUV Key and the Knight Boots. If you wanted these 2 items then save again, if you were only looking to get the achievement then reload the save now that you have it. The achievement is also cumulative, and does not need to be done all in one playthrough.