As the CEO of Goldman Sachs, Blankfein is one of the most influential people on Wall Street.

But he worked his way up from the bottom. He grew up in Brooklyn housing projects and worked his first job as a concession vendor at Yankee Stadium.

Branson, the billionaire founder of the Virgin Group, has worked for himself from day one. Although he's a bit more careful about his business decisions today.

At the age of 11, Branson says in a LinkedIn post, he and his best friend Nik Powell started breeding parakeets to sell as pets to their classmates. The birds started multiplying faster than they could sell them, so they then tried their hand in a different market. As Christmas approached, they bought small fir trees and hoped to make a profit off them once they grew big — but rabbits destroyed the trees before they could grow.

Comstock is the CMO of General Electric and oversaw the creation of the Hulu streaming service.

But before she entered the professional world, she learned the value of hard work at a Rubbermaid factory that produced kitchenware. In a LinkedIn post, she explains that she took the summer job after her freshman year of college as a break from academic work but found herself completely overwhelmed. She's still proud of learning how to work as a team to overcome the difficult months of labor.

Buffett has been interested in making and saving money since he was a kid. Today, the chairman and CEO of Berkshire Hathaway is worth an estimated $58.5 billion, making him one of the world's wealthiest people.

At the age of 14, Buffett spent his mornings delivering copies of the Washington Post. That same year, he invested $1,200 of his savings into 40 acres of farmland.

Even the leader of the free world once had a non-glamorous summer job.

As a teenager growing up in Honolulu, Obama got his first gig working the counter at Baskin-Robbins.

Winfrey's media empire made her the first female black billionaire — she's worth an estimated $3 billion today. Before she made it the top, she struggled her way out of a difficult, impoverished childhood.

When she was living with her dad in Nashville as a young teenager, she worked at a corner grocery store next to her dad's barber shop, Forbes reports.

As founder and CEO of Dell Inc., Dell enjoyed a rise to power during the heyday of the personal computer. Today, Dell is helping his company bounce back by embracing enterprise technology and cloud computing. He is worth an estimated $15.3 billion.

But before he helped make PCs mainstream, Dell got his first job scrubbing dishes for a Chinese restaurant at the age of 12.

Murdock, the 91-year-old chairman and CEO of Dole Foods, turned the company into the world's largest producer and marketer of fruits and vegetables. He's worth an estimated $2.4 billion today, but he grew up poor and dropped out of high school in the ninth grade.

After quitting school, Murdock worked at a gas station until he was drafted into the Army in 1943, Forbes reports.

Zehner is the CEO of the charity Women Moving Millions, and in 1996 she became the first female partner at Goldman Sachs.

She spent her early teens in Canada working the concession stand at games for her local farm team, the Kelowna Buckaroos. In a LinkedIn post, she says her time spent running a busy stand and making quick transactions proved to be perfect training for the Wall Street trading floor.

Pickens is the chairman of the hedge fund BP Capital Management. He showed his aggressive business savvy at a young age.

Like Buffett, Pickens was a paper boy. At the age of 12, Pickens expanded his delivery route from 28 houses to 156 by taking over his competitor's routes, according to Forbes. He has said that this taught him the value of expanding business through acquisition.

Diaz-Ortiz was one of Twitter's early hires, and today leads the company's social innovation. She's spent time turning celebrities and world leaders into influential Twitter users, and is the person who got Pope Francis to start tweeting.

As a teenager Diaz-Ortiz had spent some time babysitting but she got her first real job with the city of Berkley, California, she writes on LinkedIn. She spent most of her time promoting the city's initiative to get teenagers to stop using tobacco through fliers or speeches, but her favorite moments were police stings, where she would try to get store owners to sell her cigarettes (she was under 18).

Trump, the billionaire real estate mogul and animated television personality, grew up wealthy, but his father wanted him to learn the value of money.

As a kid, his dad would take him to construction sites and have him and his brother pick up empty soda bottles to redeem for cash, he tells Forbes. He says that he didn't make much, but it taught him to work for his money.

The former mayor of New York City is now worth an estimated $34.8 billion, but he comes from a middle-class family.

As a student at Johns Hopkins University, he worked as a parking lot attendant to help pay his loans for tuition.

Albright became the first female secretary of state, serving under President Bill Clinton. She made it into the U.S. as a political refugee from Czechoslovakia, since her anti-Soviet family was in danger from her country's communist party.

She got her first job selling bras at a department store in Denver, she tells Forbes. She adds that she probably made next to nothing, but learned how to deal with people in difficult situations.

Schwab founded the Charles Schwab Corporation, a brokerage and banking firm, and is today worth $6.1 billion. He tells Stanford's alumni magazine that he had the entrepreneurial spirit from a young age.

Schwab grew up in an upper-middle class family in Sacramento, California, but wanted to make his own money. As a kid, he bagged and sold walnuts and raised chickens in his backyard, selling some and using others for eggs to sell.

15 Billionaires Who Were Once Dirt Poor>>