Five years ago, Brock Harris was sitting on a mountain of debt, with about $50,000 in student loans and credit-card bills, making $30,000 a year and running behind in payments. These days, the 30-year-old owner of Brock Real Estate in Los Angeles owns a dozen pieces of property and has 10 real-estate agents working for him.

What happened in between?

One afternoon, he says, he found himself stuck in traffic between two luxury autos. "I knew for a fact that the lease payments were about a thousand dollars a month on each one of those cars, and at the time I was like 'A thousand dollars a month? What on earth are these people doing? They can't be working a job!'"

He says he had had enough jobs to know that "the wages are limited, the upside is limited, and I could count on a five or 10 percent wage increase a year." Mr. Harris wanted to pay off his debt, and he wanted to be able to afford one of those cars.

He began reading books about business, took a few classes and started working with a successful real-estate broker. When he was 26, Mr. Harris started his own company. Today, he drives a Toyota Prius but says he could afford fancier.

For some twentysomethings, getting ahead is not about sitting still for a better job or the next raise. It's about unrestrained ambition.

In a corporate workplace, or any institutional meritocracy, people rise largely based on their experience. But experience isn't something that someone under 30 can really claim, without raised eyebrows and evidence of some prodigal childhood enterprise. For twentysomething entrepreneurs with energy, drive and an impetuous attitude, impatience is their virtue.

"One thing I've learned from successful business owners, including my mentor, is that they have a bias towards massive action. They are always moving," says Mr. Harris. His multi-level uber-contemporary, glass and steel office space is a testament to his mission: "Keep the inventory moving, keep the housing moving, and keep the phones ringing."

Getting rich doesn't sound vulgar when you think about what being poor can mean -- huge student loans, credit-card debt, burritos for dinner (every night), and roommates who leave dirty underwear around the apartment and deny using the wireless Internet service so they don't have to pay for it.

But jumping into an entrepreneurial venture when you're twentysomething doesn't always work out. Starting a business can have its anxious moments, or even years.

Jenny Baker, now 40, of Philadelphia, started a line of educational dolls when she was 29 called the Get Set Club. Ms. Baker says she invested a quarter of a million dollars, mostly loans, and put her heart and soul into the production. "It was a real thrill," she says. But the line wasn't ultimately successful and after about six years working to get the business off the ground, she filed for personal bankruptcy. She was evicted and her car was repossessed.

"When it fell apart it was horrible," she says. "I couldn't pay people, I had to let people go, and I was living in the same space the office was in." Ms. Baker was so absorbed in building her business that she lost track of many friends. "It was a very lonely time because nobody my age was really going through that."

During the dot-com era, many young entrepreneurs got swept up by the idea of making millions through new ventures on the Internet, and many did indeed fare well but many also lost their shirts. According to preliminary estimates from the U.S. Census Bureau, around 9% of business owners were age 34 or under in 2002, the most recent year for which figures are available.

Still, Internet entrepreneurship continues. Dalton Caldwell, the 26-year-old co-founder of Imeem.com, an instant messaging/social media service, says running a business has disrupted the live/work balance in his life. "Given work hours, [my] travel schedule, meetings, and the kind of people I interact with on a daily basis, I have a bizarre lifestyle for a twentysomething," he says. "When I started Imeem, I basically said goodbye to anything resembling a normal life."

As he was creating the idea for Imeem.com, Mr. Caldwell was broke, and working out of an apartment until four in the morning every night doing computer coding to launch the project. He works out of an office now, in Palo Alto, Calif., has 21 employees and makes more than $100,000 a year. "I want, instead of being kind of a square peg in a round hole in an organization, to actually be rewarded for how quickly I want to move on things, and how ambitious I am in the projects I undertake," says Mr. Caldwell, who dresses casual and shows up to work at 10:30.

The funding for Imeem.com came from Morgenthaler Ventures, a venture capital firm in Menlo Park. Ken Gullicksen, a partner, worked with Mr. Caldwell and his partner Jan Jannink to get financing for their project. They met regularly at Starbucks, before the founders rented a garage nearby to get out of their apartments and develop the business.

Mr. Gullicksen says many of the businesses his firm funds, which include media, biotech, medical instruments, and information-technology upstarts, demand well-established industry experience from their founders. "If you're not somebody who's been in the industry for 10 years and has a good understanding of companies in your space and a strong Rolodex of contacts to go sell your product into, you'd really be struggling," he says.

But Mr. Gullicksen says he decided to take the risk with Imeem.com, in part because Mr. Caldwell's age is an asset in the case of a business that targets a young audience of Web users who also have a MySpace page or a blog. "It's such an incredibly ambitious vision that a little bit of not knowing what you're getting into is helpful here. If he did know, it would be daunting and probably less ambitious."

If these young entrepreneurs are so talented, why can't they apply themselves within an existing organization and reap similar rewards? Perhaps they could and perhaps it would be easier but it could also take a lot longer. Sometimes the drive to succeed can trump the worries about not making it.

"You can't be one of those people who sends Google or Yahoo your crazy idea and expect them to hire you and let you build it," says Mr. Caldwell. "That's just not how it works."