Nellie Thomas sold ammunition illegally on the South side of Chicago. He made a good living—in cash. And that was his problem. The money was driving him crazy. He was ashamed to tell his family how he earned it, he was afraid he'd be robbed, and he didn't know how to get rid of it. So he kept it in big black garbage bags which he hid around his house and yard. Then one day, he came up with the perfect way to get rid of the money. Sudhir Alladi Venkatesh tells Nellie's story. Sudhir is a sociology professor at Columbia University and author of Off the Books: The Underground Economy of the Urban Poor. (15 minutes)