Aspiring entrepreneurs must constantly navigate the tension between doing what they love and the realities of the market. Sometimes those interests align: Bill Gates and Paul Allen loved to write software, and happened to be doing it at the dawn of a multibillion-dollar industry. But more often, entrepreneurs walk a high wire between pursuing passion and the market opportunity where they have the greatest chance to succeed.

To Gary Vaynerchuk, who is building a small empire on his own obsession with wine, the Internet, and business, passion is the market opportunity. His new book, Crush It!, describes how to combine passion, hard work, and technology to create a successful niche business.

"It's insane to me to ask anybody to be what they're not," Vaynerchuk says in an interview. "Know what you know the best, love the most. That's always going to be the answer to the thing that you have the best shot at winning at."

His road map is clear, if not easy. Pick a specialty you love, build your reputation as an expert, pump out content online, and eventually make money by selling advertising, niche products, or services such as consulting or speaking. Success demands relentless "hustle"—one of his favorite words—and patience to press on when less passionate entrepreneurs would quit.

Vaynerchuk, 33, is proof that passion and hustle can breed success. He turned his family's small New Jersey liquor store into a wine empire that grosses over $60 million a year; more than 100,000 viewers watch his daily video blog; he's a sought-after speaker; and he's signed on to write nine more business books for HarperCollins (NWS). But should entrepreneurs follow his advice?

Passion Plus Confidence
Some evidence suggests that passionate entrepreneurs perform better. A six-year study that sampled companies in the architectural woodworking industry found that passion and "self-efficacy"—a measure of confidence in one's own ability—were the biggest predictors of growth. "Those that had high self-efficacy and who had passion for their work were more likely to succeed," says J. Robert Baum, a professor at the University of Maryland and co-author of the study. But both elements were necessary. "One without the other didn't point to success."

While passion may be an important personal trait, other conditions beyond the character of the entrepreneur affect how well a business performs. "The evidence is that your odds are better if you're responding to a problem or need in the marketplace than if you're saying I'm really into X so I'm going to start a business around X," says Scott Shane, professor of entrepreneurship at Case Western Reserve University.

But Shane says passion often goes hand-in-hand with hard work (Vaynerchuk's "hustle") and the drive to put in long hours does improve a company's odds of success. However, picking more favorable industries—think software vendors instead of restaurants—has a greater effect. "To say passion is better, when what you're passionate about is a lousy opportunity, is risky," he says.

Of course, the Vaynerchuk model is less about building juggernaut businesses than it is about liberating people from work they don't like and finding ways to make money doing what they love.

Nonfinancial Returns
Paula Davis had been making soap by hand as a hobby for four years when her marriage ended. The single mother considered returning to her old job as a legal assistant, but she hated the thought of putting her young kids in day care while she went to work full time. So she decided to sell her artisan soaps, forming the Canyon Creek Soap Co. in Amarillo, Tex., in 2004. "I still really only thought it would just be something small that would make ends meet until the children were older," she says.

Five years in, Davis is still making soap, selling wholesale and private-label products in stores, along with retailing through her Web site. The business is modest—in her best year, her revenue was $65,000, she says. She would make more working at her old profession, but she values the nonfinancial returns of her venture. "I wouldn't have had time for my children," Davis says. "Too many people choose money over lifestyle in our society."

And there's plenty of evidence to suggest that people who work for themselves are generally happier. More than giving concrete business advice, Vaynerchuk wants people to rethink their priorities in both business and life. Seeking profit instead of passion, he says, is a recipe for failure. "People are chasing cash, not happiness," he says. "When you chase money, you're going to lose. You're just going to. Even if you get the money, you're not going to be happy."
By John Tozzi  who covers small business for BusinessWeek.com