Marcus & Millichap Inc.’s website has more than 2,800 commercial properties for sale. The most expensive is a hotel on the New Jersey side of the Lincoln Tunnel for $50 million. The cheapest: a Memphis apartment building listed at $55,000.

The company’s collection of retail shops, offices and apartments has made it the country’s leader in private client transactions, which generally are below $10 million and make up the bulk of U.S. commercial real estate sales. It’s also made the brokerage’s founder, George Marcus, a billionaire.

Marcus & Millichap has more listings than any of its competitors, and its brokers closed more deals than any other U.S. commercial brokerage in 2014: 7,667 transactions with a value of more than $33 billion.

“They are the industry leader,” said Mitchell Germain, a New York-based senior analyst with JMP Securities. “They have a database nobody else can replicate.”

Marcus controls a $1.9 billion fortune, according to the Bloomberg Billionaires Index. He’s never appeared on an international wealth ranking. Gina Relva, a spokeswoman for the Calabasas, California-based business, said he declined to comment on his net worth.

Marcus & Millichap’s revenue increased 28 percent in the first three months of 2015 as sales volume jumped 30 percent to $8.1 billion. The billionaire owns 55 percent of the company, which has almost quadrupled in value since its October 2013 initial public offering, outpacing larger peers such as CBRE Group Inc. and Jones Lang LaSalle Inc.

Biggest Landlord

Marcus also created Essex Property Trust Inc., the West Coast’s biggest apartment landlord, which owns more than 50,000 units from Seattle to San Diego. He controls about 2.4 percent of the $15 billion real estate investment trust.

The billionaire was born in Euboea in 1941, a Greek island about 60 miles north of Athens. The family immigrated to the U.S. when he was four and moved to San Francisco. After working as a broker at Grubb & Ellis in San Jose, he left to set up his own shop in 1971, seeking to overhaul the prevailing informality and opaqueness of the industry.

“Real estate was almost a fraternity club,” Marcus said in a June 2011 interview with the Palo Alto Weekly. “Your uncle or your father or someone in the community knew you and your family and you sat at some real estate office and they told you they want to sell this building or that building and you brought them some offers.”