To the casual observer, entrepreneurship may seem glamorous: Those who start companies have infinite freedom and are their own bosses. Newspaper headlines are full of tales of billion-dollar acquisitions, IPOs, fancy club events and hip co-working spaces.

But lurking behind the scenes is a high failure rate (75 percent for venture-backed start-ups), the emotional roller coaster for entrepreneurs who put it all on the line and the immense number of hours it takes them before making their first dollar. 

For these six entrepreneurs who immigrated to the United States, starting a business wasn’t easy. For each, the path was long and complicated, but they persisted.

Review these entrepreneurs’ toughest moments and note their tenacity.

Related: Gary Vaynerchuk on His Roots As an Entrepreneur

A love of technology. Bo Lu is the eldest son of Chinese immigrants who moved to Morgantown, W.V., after leaving China following the Tiananmen Square massacre. Struggling with unemployment, the family scavenged broken household electronics left behind by other Morgantown families in their driveways. Bo Lu’s engineer parents made a living out of restoring them.

Bo Lu fell in love with technology and also became an engineer. After working for Microsoft, he launched in 2011 San Francisco-based FutureAdvisor, an online investment-management company. Accepted into the Y Combinator accelerator program and backed by Sequoia Capital, his company now helps retail investors track $11.3 billion in assets via using his software.

Bringing retail to Africa. Chris Folayan, a programmer, moved from Nigeria to the San Francisco Bay area to attend college. Every time that Folayan visited friends and family in Nigeria, people asked for products from the States or the United Kingdom. He started MallForAfrica in San Francisco to help African residents buy products from the U.S. and U.K.  

In launching his company, Folayan had to confront stereotypes (that the African continent is magnet for cyber-crime and fraud) and misconceptions (that all Africans are poor and starving). MallForAfrica has beome a multimillion-dollar enterprise, with a network of 70 sites offering more than 7 billion items for sale.

Helping others launch businesses. In 1976, 5-year-old Nellie Akalp immigrated to the U.S. from Iran with her family. Despite linguistic challenges, her parents immediately launched a Persian antique shop.

Akalp was inspired by her parents' entrepreneurship. Fresh out of law school, she launched an online business with her husband after purchasing a domain name for $100. In 2005, they sold that company, a legal-document filing service that helped entrepreneurs file paperwork, to Intuit for $20 million.

Although Akalp and her husband could have retired, they co-founded another venture in 2009: CorpNet, based in Westlake Village, Calif., helps entrepreneurs incorporate limited partnerships.

A focus on repair. Vladimir Gendelman immigrated to the U.S. from the Soviet Union as a teenager, dreaming of someday owning a business. He held a succession of jobs after moving to Detroit: He worked as an ice-arena custodian, a demolition worker, a pizza-delivery person, a door-to-door salesman, a carpet merchant and a software developer.

After acquiring experience in computer repair, Gendelman started his own business in 2003, doing just that, with little credit or funds. In 2012, his business lost 80 percent of his website traffic due to Google's changing of its algorithms.

Instead of filing for bankruptcy, though, Gendelman borrowed money to navigate through the hard times. He listened to his customers and their needs and ventured into a different area. Since 2013, his new business Company Folders in Keego Harbor, Mich., has been running smoothly, allowing customers to custom print folders.

A pizza empire in Georgia. The day after DJ Patel graduated college in India in 1987, he flew to the United States with just $100 in his pocket. He worked long hours at blue-collar jobs and saved up for years so he could own a small percentage of his first business. Now almost three decades later, the 49-year-old oversees six successful Marco’s Pizza franchises, in the Atlanta area and in Toledo, Ohio. Since venturing into the pizza franchise world in 2009, Patel has become a leader in Georgia’s Indian entrepreneur community and now mentors a dozen franchise owners.  

A pair of restaurants for a duo. Dexter Bartholomew and his wife, Djenane, immigrated to the United States as children, from Grenada and Haiti respectively, marrying in 1997, a year after they met, and raising three children.

After holding various roles at franchise businesses, the couple bought two franchises of their own in 2011: Golden Corral restaurants in Egg Harbor Township, N.J. Like Patel, they also faced the challenge of having a lack of money, little understanding of English and not knowing very many people. They followed a similar path similar to Patel's. They worked in various roles (such as cashier and janitor) at franchise business until they  saved up enough to start their own business.

Today they say are learning more about the restaurant business all the time and are becoming well-rounded entrepreneurs. 

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