Federal agents set up a fake university to expose immigration fraud and arrested 21 people, some of who acted as brokers for more than 1,000 foreigners looking to maintain student and work visas, prosecutors said Tuesday. Officials said those accused were aware that the University of Northern New Jersey did not exist. Most foreign nationals who were involved in the ruse came from China and India. The nationals who were affected will not be prosecuted, officials said. “This was just another stop on the ‘pay-to-stay’ tour,” said Paul Fishman, U.S. Attorney for New Jersey.