John Catsimatidis was six months old when his parents left the Greek island of Nisyros for New York. His father found wo...

John Catsimatidis was six months old when his parents left the Greek island of Nisyros for New York. His father found work at a restaurant in Harlem, and the family built a modest life from there. Nobody would have predicted that the boy from that apartment would one day be worth $4.8 billion. He enrolled at New York University to study electrical engineering, and to cover expenses he took a part-time job at a small grocery store. What started as a side gig turned into something else entirely. He started watching which products moved, how fast inventory turned over, and what customers actually wanted, treating the store like a classroom in applied business. The owner noticed his instincts and offered him a 50% stake for $10,000. Catsimatidis didn't have the money, so he negotiated to pay in ten monthly installments of $1,000, financed by the store's own profits. Miss one payment and he'd lose his share. He didn't miss any. Sales climbed fast enough that he faced a decision no business school would have scripted. He was a single semester from graduation, just eight credits away from his engineering degree, and he walked away. He never went back for the diploma. By age 25, he had ten supermarkets across Manhattan generating around $25 million a year in annual sales, with no bank debt. He'd persuaded suppliers to extend him credit, using incoming sales to pay them back, essentially turning his supply chain into his own financing operation. When New York City hit its fiscal collapse in the mid-1970s, most investors fled. Catsimatidis put roughly $5 million from his supermarket profits into Manhattan real estate in 1977. By his own account, that portfolio was worth around $100 million five years later. A later bet on aviation, including the 1984 purchase of Capitol Air, went badly and ended in bankruptcy. But working through that failure brought him into contact with United Refining, a struggling oil company. He bought control of it, and petroleum became one of the central pillars of his fortune. His Red Apple Group eventually grew to span groceries, real estate, energy, and media, including the well-known Gristedes supermarket chain. His net worth today si...