Nearly three decades ago, Tomas Gorny came to the U.S. as a Polish immigrant living on $3 a day, after rent and transportation costs. He worked up to 100 hours per week at three different jobs to make ends meet, he says.

Today, the 49-year-old Gorny is the founder of multiple tech businesses, including a cloud-based business communications company called Nextiva that was most recently valued at $2.7 billion. Gorny, the company's CEO, has a net worth exceeding $1 billion, according to a Nextiva spokesperson.

Gorny attended college in Germany while dreaming of moving to the U.S. to start a tech business. When a friend invited him to Los Angeles to help build a website-hosting startup in 1996, he took the chance, dropping out a few months before graduating and bringing his life savings of around $15,000, he says.

The money disappeared "super quickly" — spent on housing, legal fees for a work visa and a "piece of crap" car that broke down within months, Gorny tells CNBC Make It.

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His startup, called Internet Communications, wasn't bringing in any money yet, so Gorny spent nights and weekends working as a parking valet and commercial carpet cleaner. After rent and transportation costs, he had only a few dollars per day for food and other necessities, he says.

"I was living off McDonald's," says Gorny. "Once a week, I remember, my friend and I, we went to Sizzler [and] got all-you-can-eat for $7.99 ... I always over-ate, because it was this one time a week I got to really enjoy [my meal]."

Two years later, his $3 per day turned into a net worth above $1 million, he says. Three years after that, he lost nearly all of it — before making his money back again, ultimately becoming a billionaire in the process.

Making, and losing, millions

Gorny's first startup may have started slow, but the internet boom meant that every business in the world needed help building a website. Early-stage web-hosting companies were ripe for acquisition, says Gorny.

In 1998, Internet Communications was acquired by Interliant in a deal worth roughly $6 million in cash and stock, according to Gorny. As a minority owner, he walked away with over $1 million, and when Interliant went public in 1999, the stock he earned in the deal was worth several million dollars, he says.

"I went from literally living on $3 a day to becoming, now, a millionaire," says Gorny. "I bought a car for $40,000 and I put a mortgage loan payment on a house, and I reinvested the rest of my proceeds in [a new internet advertising startup]."

When the dot-com boom bottomed out in 2001, Gorny's newer startup flopped — and Interliant went bankrupt, sending his stock value plummeting to just $6,000, he says.

"Three years [after the sale], I didn't know how to pay my next mortgage," says Gorny.

Distraught and financially struggling, he decided to use the experience as motivation — partially because he had no other choice, he notes: "I love the idea of being an underdog. It's just, kind of, in my DNA."

'I just wanted to make $5,000 a month to survive'

Gorny sold his devalued stock and put the thousands of dollars toward buying two internet servers for a new venture called Ipower, which built software tools for people to create their own websites without much technical knowledge.

The tech industry wasn't exactly in financially healthy shape, but people and businesses were still joining the internet for the first time, Gorny says. Within months, Ipower had thousands of new customers, making it one of the country's fastest-growing web-hosting companies, he adds.

In 2006, Gorny launched Nextiva — the company responsible for making him a billionaire today, largely off the strength of its 100,000-business client base and $200 million in recent funding from Goldman Sachs. In 2007, he sold Ipower to IT services company Endurance International in a deal reportedly worth $100 million.

Gorny says he was primarily motivated by the mental challenge of understanding a common problem deeply enough that customers would pay for his solution — rather than accruing wealth. "I just wanted to make $5,000 a month to survive, pay my mortgage," he says.

His experience scraping by on $3 per day made it easier for him to stick to those convictions, instead of trying to make a quick buck with more short-sighted ventures, he adds: "I could sleep on somebody's couch if it had come down to it."

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