Cashed Checks

"The rise of check cashing places is directly tied to the growth in illegal immigration. How do you think illegal immigrants manage their finances? They can't open bank accounts because you need SSN's to do that. But they have bills to pay like anyone else. So they have to go to check cashing places where the cash they have or the checks they receive can enter the financial system. If you think of the money they collect for work as "illegal", this is how that money gets laundered."

via a MeFi comment.