Billionaire Bill Ackman, founder of Pershing Square, said that a top candidate for his exclusive investment team has spent time in a top-notch investment banking program as well as a private equity company. Ackman, speaking on an online conference hosted by Bloomberg, warned that his firm doesn't hire many investors — currently, his team has just seven people, including himself. "We're really a private equity firm that's investing solely in public markets," he said. Visit Business Insider's homepage for more stories.