Some people know what they want to do from an early age and focus on it relentlessly.
Others reinvent themselves, changing careers and industries until they find something that works.
Billionaire Mark Cuban struggled when he first started, writing in "How To Win At The Sport Of Business" that "when I got to Dallas, I was struggling — sleeping on the floor with six guys in a three-bedroom apartment."
As a reminder that the path to success is not always linear, we've highlighted what Richard Branson, Martha Stewart, and other fascinating and successful people were doing at age 25.
Martha Stewart was a stockbroker for the firm of Monness, Williams, and Sidel, the original Oppenheimer & Co.
Before her name was known by every American household, Martha Stewart actually worked on Wall Street for five years as a stockbroker. Before that, she was a model, booking clients from Unilever to Chanel.
"There were very few women at the time on Wall Street … and people talked about this glass ceiling, which I never even thought about," Stewart said in an interview with PBS' MAKERS series. "I never considered myself an unequal and I think I got a very good education being a stockbroker."
In 1972, Stewart left Wall Street to be a stay-at-home mom. A year later, she started a catering business.
Mark Cuban was a bartender in Dallas.
At age 25, Cuban had graduated from Indiana University and had moved to Dallas. He started out as a bartender, then a salesperson for a PC software retailer. He actually got fired because he wanted to go close a deal rather than open a store in the morning. That helped inspire him to open his first business, MicroSolutions.
“When I got to Dallas, I was struggling — sleeping on the floor with six guys in a three-bedroom apartment,” Cuban writes in his book “How to Win at the Sport of Business.” “I used to drive around, look at the big houses, and imagine what it would be like to live there and use that as motivation.”
Lloyd Blankfein was an unhappy lawyer.
Blankfein didn't take the typical route to finance. He actually started out as a lawyer. He got his law degree from Harvard at age 24, then took a job as an associate at law firm Donovan Leisure.
"I was as provincial as you could be, albeit from Brooklyn, the province of Brooklyn," Blankfein told William Cohen at Fortune Magazine.
At the time, he was a heavy smoker and occasional gambler. Despite the fact that he was on the partner track at the firm, he decided to switch to investment banking, joining J. Aron at the age of 27.
Ralph Lauren was a sales assistant at Brooks Brothers.
He was born Ralph Lifshitz in the Bronx, New York, but changed his name at the age of 15. He went on to study business at Baruch College and served in the Army until the age of 24 when he left to work for Brooks Brothers.
At 26, Lauren decided to design a wide European-styled tie, which eventually led to an opportunity with Neiman Marcus. The next year, he launched the label "Polo."
JK Rowling came up with the idea for the Harry Potter series on a train.
In 1990, Rowling was 25 years old when she came up with the idea for Harry Potter during a delayed four-hour train ride.
She started writing the first book that evening, but it took her years to actually finish it. While working as a secretary for the London office of Amnesty International, Rowling was fired for daydreaming too much about Harry Potter and her severance check would help her focus on writing for the next few years.
During these years, she got married, had a daughter, got divorced, and was diagnosed with clinical depression before finally finishing the book in 1995. It was published in 1997.
Jay-Z was already in the rap scene, but was 'relatively anonymous.'
Born Shawn Carter, Jay Z grew up in a housing project in Brooklyn, New York and became known as "Jay Z" at the age of 20. For the next few years he appeared alongside various other rappers, but "remained relatively anonymous" until he founded the record label Roc-A-Fella Records at the age of 27 with two other friends. The same year, Jay Z released his first album, "Reasonable Doubt."
Warren Buffett was working as an investment salesman in Omaha.
In his early 20s, Buffett worked as an investment salesman for Buffett-Falk & Co. in Omaha before moving to New York to be a securities analyst at age 26. During that year, he started Buffett Partnership, Ltd., an investment partnership in Omaha.
New York just wasn't for him, Buffett told NBC. "In some places it's easy to lose perspective. But I think it's very easy to keep perspective in a place like Omaha."
Ursula Burns started out as an intern, but worked her way up at Xerox throughout her 20s.
Burns overcame a tough upbringing in a New York City housing project to get a degree in Mechanical engineering from the Polytechnic Institute of NYU, then a masters from Columbia University.
Since then she's been a Xerox lifer. She started as an intern at age 22 in 1980, and joined full time a year later after getting her masters. She rose rapidly through the ranks, working in various product development roles and was named CEO in 2009.
"When I came to work at Xerox, I just chose to work. Somebody said 'how about this?' And I said OK, and I would go do that in the lab," Burns said in an interview for the PBS documentary, "Makers." "Then somebody said how about doing some business planning. Then I started leaning more towards larger global systems problems. And systems problems are the business."
Mark Zuckerberg's Facebook was cash positive for the first time and hit 300 million users.
Mark Zuckerberg had been hard at work on Facebook for five years by the time he hit age 25. In that year — 2009 — the company turned cash positive for the first time and hit 300 million users. He was excited at the time, but said it was just the start, writing on Facebook that "the way we think about this is that we're just getting started on our goal of connecting everyone."
The next year, he was named "Person of the Year" by Time magazine.
Tina Fey was a child-care registrar at the Y.M.C.A before joining famed improv troupe Second City.
After graduating from the University of Virginia, Fey moved to Chicago and hung around acting workshops and even worked as the child-care registrar at a Y.M.C.A before improv troupe Second City invited her to join.
Fey told The New Yorker that she joined Second City because she "knew it was where a lot of S.N.L. people started," and in 1997 she sent scripts to Saturday Night Live producer Lorne Michaels who then hired her as a writer.
Tim Allen was arrested and served the next two years in federal prison.
While working as a stand up comedian, Allen was arrested at 25 in an airport for possessing more than 650 grams of cocaine. He pleaded guilty to drug trafficking charges and received two years instead of life in prison for providing the names of other dealers.
The experience was so bad that he was forced to turn himself around. He told Esquire, "When I went to jail, reality hit so hard that it took my breath away, took my stance away, took my strength away. I was there buck naked, humiliated ... this is a metaphor. My ego had run off. Your ego is the biggest coward."
Allen became known to the public for his role on the sitcom "Home Improvement," which premiered in 1991.
Richard Branson had already started the Virgin Records record label.
At age 20, Branson opened his first record shop, then a studio at 22 and launched the label at 23. By 30, his company was international.
Those early years were tough, he told Entrepreneur: "I remember them vividly. It's far more difficult being a small-business owner starting a business than it is for me with thousands of people working for us and 400 companies. Building a business from scratch is 24 hours, 7 days a week, divorces, it's difficult to hold your family life together, it's bloody hard work and only one word really matters — and that's surviving."
To see the full list of What Extremely Successful People Were Doing At Age 25, click here.