Kenny Troutt, the founder of Excel Communications, paid his way through college by selling life insurance.
Net worth: $1.5 billion
Troutt grew up with a bartender dad and paid for his own tuition at Southern Illinois University by selling life insurance. He made most of his money from phone company Excel Communications, which he founded in 1988 and took public in 1996. Two years later, Troutt merged his company with Teleglobe in a $3.5 billion deal.
He's now retired and invests heavily in racehorses.
Starbucks' Howard Schultz grew up in a housing complex for the poor.
Net worth: $2.3 billion
In an interview with British tabloid Mirror, Schultz says: "Growing up I always felt like I was living on the other side of the tracks. I knew the people on the other side had more resources, more money, happier families. And for some reason, I don't know why or how, I wanted to climb over that fence and achieve something beyond what people were saying was possible. I may have a suit and tie on now but I know where I'm from and I know what it's like."
Schultz ended up winning a football scholarship to the University of Northern Michigan and went to work for Xerox after graduation. Shortly after, he took over a coffee shop called Starbucks, which at the time had only 60 shops. Schultz became the company's CEO in 1987 and grew the coffee chain to more than 16,000 outlets worldwide.
Investor Ken Langone's parents worked as a plumber and cafeteria worker.
Net worth: $2.6 billion
To help pay for Langone's school at Bucknell University, he worked odd jobs and his parents mortgaged their home.
In 1968, Langone worked with Ross Perot to take Electronic Data Systems public. (It was later acquired by HP.) Just two years later, he partnered with Bernard Marcus to start Home Depot, which also went public in 1981.
Born into poverty, Oprah Winfrey became the first African American TV correspondent in Nashville.
Net worth: $3 billion
Winfrey was born into a poor family in Mississippi, but this didn't stop her from winning a scholarship to Tennessee State University and becoming the first African American TV correspondent in the state at the age of 19.
In 1983, Winfrey moved to Chicago to work for an AM talk show which would later be called "The Oprah Winfrey Show."
John Paul DeJoria, the man behind a hair-care empire and Patron Tequila, once lived in a foster home and his car.
Net worth: $3.2 billion
Before the age of 10, DeJoria, a first generation American, sold Christmas cards and newspapers to help support his family. He was eventually sent to live in a foster home and even spent some time in a gang before joining the military.
With a $700 dollar loan, DeJoria created John Paul Mitchell Systems and sold the shampoo door-to-door while living in his car. He later started Patron Tequila, and now invests in other industries.
Mega-resort owner Kirk Kerkorian dropped out of school in the eighth grade to become a boxer.
Net worth: $4 billion
To financially help his Armenian-immigrant family, Kerkorian dropped out of school in the eighth grade and later would become a boxer called "Rifle Right Kerkorian." During World War II, Kerkorian worked for Britain's Royal Air Force. He eventually turned his interest to constructing many of Las Vegas' biggest resorts and hotels.
At one time, businessman Shahid Khan washed dishes for $1.20 an hour.
Net worth: $4.4 billion
He's now one of the richest people in the world, but when Khan came to the US from Pakistan, he worked as a dishwasher while attending the University of Illinois. Khan now owns Flex-N-Gate, one of the largest private companies in the US, the NFL's Jacksonville Jaguars, and Premier League soccer club Fulham.
Forever 21 founder Do Won Chang worked as a janitor, gas station attendant, and in a coffee shop when he first moved to America.
Net worth: $5.5 billion
The husband-and-wife team — Do Won Chang and Jin Sook — behind Forever 21 didn't always have it so easy. After moving to America from Korea in 1981, Do Won had to work three jobs at the same time to make ends meet. They opened their first clothing store in 1984.
Forever 21 is now an international, 480-store empire that rakes in around $3 billion in sales a year.
Ralph Lauren was once a clerk at Brooks Brothers dreaming of men's ties.
Net worth: $8.2 billion
Lauren graduated high school in the Bronx, New York, but later dropped out of college to join the Army. It was while working as a clerk at Brooks Brothers that Lauren questioned whether men were ready for wider and brighter designs in ties. The year he decided to make his dream a reality, 1967, Lauren sold $500,000 worth of ties. He started Polo the next year.
Steel tycoon Lakshmi Mittal came from modest beginnings in India.
Net worth: $13.2 billion
A 2009 BBC article says the ArcelorMittal CEO and chairman, who was born in 1950 to a poor family in the Indian state of Rajasthan, "established the foundations of his fortune over two decades by doing much of his business in the steel industry equivalent of a discount warehouse."
Today Mittal runs the world's largest steel making company and is a multibillionaire.
Luxury goods mogul Francois Pinault quit high school in 1974 after being bullied for being poor.
Net worth: $14.2 billion
Pinault is now the face of fashion conglomerate Kering (formerly PPR), but at one time, he had to quit high school because he was teased so harshly for being poor. As a businessman, Pinault is known for his "predator" tactic, which includes buying smaller firms for a fraction of the cost when the market crashed. He eventually started PPR, which owns high-end fashion houses including Gucci, Stella McCartney, Alexander McQueen, and Yves Saint Laurent.
Leonardo Del Vecchio grew up in an orphanage and later worked in a factory where he lost part of his finger.
Net worth: $19.1 billion
Del Vecchio was one of five children who was eventually sent to an orphanage because his widow mother couldn't care for him. He would later work in a factory making molds of auto parts and eyeglass frames.
At the age of 23, Del Vecchio opened his own molding shop, which expanded to become the world's largest maker of sunglasses and prescription eyewear with brands like Ray-Ban and Oakley.
Legendary trader George Soros survived the Nazi occupation of Hungary and arrived in London as an impoverished college student.
Net worth: $24 billion
In his early teens, Soros posed as the godson of an employee of the Hungarian Ministry of Agriculture in order to stay safe from the Nazi occupation of Hungary. In 1947, Soros escaped the country to live with his relatives in London. He put himself through the London School of Economics working as a waiter and railway porter.
After graduating, Soros worked at a souvenir shop before getting a job as a banker in New York City. In 1992, his famous bet against the British pound made him a billion dollars.
After his father died, business magnate Li Ka-shing had to quit school to help support his family.
Net worth: $28.3 billion
Ka-shing fled mainland China for Hong Kong in the 1940s, but his father died when he was 15, leaving Ka-shing responsible for supporting his family. In 1950, he started his own company, Cheung Kong Industries, which manufactured plastics at first but would later expand into real estate.
College dropout Sheldon Adelson grew up sleeping on the floor of a Boston tenement house.
Net worth: $28.8 billion
Adelson, the son of a cab driver, grew up in Dorchester, Massachusetts, and began selling newspapers at the age of 12, reports Bloomberg Businessweek.
A Forbes profile of the billionaire says years later, after dropping out of the City College of New York, Adelson "built a fortune running vending machines, selling newspaper ads, helping small businesses go public, developing condos and hosting trade shows."
Adelson lost almost all of his money in the Great Recession, but he earned much of it back in the following years. He now runs Las Vegas Sands, the largest casino company in the world, and is considered the most high-profile political donor in America, says Forbes.
Oracle cofounder Larry Ellison dropped out of college after his adoptive mother died, and he held odd jobs for eight years.
Net worth: $51.3 billion
Born in Brooklyn, New York, to a single mother, Ellison was raised by his aunt and uncle in Chicago. After his aunt died, Ellison dropped out of college and moved to California to work odd jobs for the next eight years. He founded software development company Oracle in 1977, which is now one of the largest technology companies in the world.
This September he announced his plans to step down as Oracle's CEO.