Martin Nussbaum, 37, Founder, Slate Property Group

Growing up in Johannesburg and moving at age 5 with his three siblings to Cranford, NJ, it helped that Martin Nussbaum (snapped on Saturday afternoon on the LES with his wife, Sharon Nussbaum) was sports obsessed. Now when he runs around finding mid-market multifamily, mixed-use, and development properties to buy in Manhattan and Brooklyn, he can pretend it's the soccer he once played aggressively five hours a day.

He was a founder of Silverstone Property Group five years ago, where he acquired and developed almost $800M in assets, and in October he started yet another company, Slate Property Group.

Already he's amassed more than $100M in property from the Upper East and West Sides to the East and West Villages, Chelsea, Gramercy Park, and across the water to Williamsburg, Park Slope, and Dumbo. With 10 colleagues, he identifies value-add and development deals, and he expects the firm will double in size this year.

Pre-med in college, he took a year off to try out the field at Long Island Jewish Hospital and quickly discovered that business came more naturally. He landed as an analyst at a real estate investment banking firm doing financial modeling but realized he didn't want to sit at a desk all day. He also came to understand that the real world is more important to him than abstract numbers: He once made what he thought was a perfect presentation, only to be told the returns were crazy; he'd moved a decimal point.

Working the next six years for a family office out of NJ put him in the thick of things: leasing, operations, construction, and acquisitions for retail, residential, and single-family homes. He loved it.

Creating his own companies is one of his life fulfillments. But now there's another. Today, besides playing weekend basketball and sneaking out to Knicks games when he can, he's also a busy family man with four daughters between 20 months and eight years.