Blackstone Group – started with less than $1m
From Business Insider http://www.businessinsider.com.au/the-most-powerful-people-in-the-world-2015-11?r=US&IR=T#/#40-ban-ki-moon-10
41. Steve Schwarzman
Title: Founder and CEO, Blackstone Group
Country: US
Age: 68
Steve Schwarzman is the unparalleled king of private equity, with a fortune of $11 billion that includes splashy homes in Manhattan, the Hamptons, Jamaica, and Saint-Tropez. His vaunted buyout firm Blackstone Group is the largest on earth, with $334 billion in assets under management, and it has completed some of the most high-profile acquisitions in the industry. The company’s $26 billion leveraged buyout of the Hilton hotel chain in 2007 is considered by some the most profitable of all time.
Schwarzman had a short but prosperous career with investment bank Lehman Brothers before leaving in 1985 to start Blackstone with ousted Lehman CEO Peter Peterson. They opened shop with $400,000, but Schwarzman gained a reputation as savvy and lucrative dealmaker, and Blackstone grew into a juggernaut. In 2014 it generated a record $7.5 billion in revenue. Never satisfied, Schwarzman wants Blackstone to double in size in the next eight years. Schwarzman donated $150 million in May to build a student commons at Yale.