Dead Rising 2: Off the Record introduces a new mode called the Sandbox Mode, which removes the time limit and lets you explore the malls, casinos and restaurants at your own pace. In Sandbox Mode, you can complete different challenges placed throughout the city.
Challenges can make you collect things, be vehicle-based or even zombie-massacres. Completing these wins you cash, and the higher your rank, the more cash you get. This cash can then be used at pawn shops and vending machines around Fortune City.