Building a business from nothing to $1 billion-plus requires more than just a good idea and hard work. Forbes spoke with four billionaire CEOs who started from scratch, learned from their prior mistakes, overcame long odds and created notable companies that are thriving. Each of them operates in a different industry—telecom, fintech, construction and IT services—and each founder brings their own perspective to running and scaling an enterprise. All share the same goal: building a resilient business that delivers on its promises and keeps customers coming back for more.

One leadership principle that John Fish has embraced in building Boston-based Suffolk into a $7 billion (2024 revenue) business is that people have to be willing to make mistakes.

“It’s humility. That’s the biggest thing,” says Fish, age 65.

That’s why years ago he created a “No Fault Culture” at his company. Employees are encouraged to take risks and do things differently, without worrying about short-term costs. “If we don’t innovate we’ll die,” says Fish. That’s why Suffolk has gambled heavily on robots on construction sites and embraced generative AI to help with everything from scheduling to architectural and engineering designs.

Fish first adopted this flexible mindset around 2008 during the Great Recession. In just four hours one September day shortly after Lehman Brothers collapsed, the then-$2 billion (revenue) Suffolk lost $1 billion in backlog as customers suddenly canceled plans to build. Fish didn’t know how he’d make payroll, but he knew that his company would not survive unless it did things differently. Rather than look to other companies in the construction category, he started studying firms outside his industry, including Google, Apple, Microsoft and Amazon. It was around that time that he decided that Suffolk would start leveraging data to hone in on its competitive edge. Fish began to invest heavily in data and technology.

In 2017, he hired MIT grad and McKinsey & Company data scientist Jit Kee Chin as Chief Data Officer. He also brought on 39 analysts to pour through historical data from hundreds of projects and created a mission control center at its headquarters where the findings are studied to help teams make better business decisions. Think Moneyball for construction: data captured from jobsites is monitored on everything from safety to cost to project delays; generative AI then evaluates the findings to spot red flags, by predicting which sites might have safety risks or are more likely to go over budget.

“You can’t manage what you can’t measure,” says Fish.

Part of Suffolk’s strategy has always been to diversify across regions and sectors to soften the blow in case any one part of the business falters. This flexible approach has also helped the company pivot into new projects. Seven years ago, mixed-use commercial/residential represented 80% of Suffolk’s revenue. Then Covid and the work from home trend hit office construction hard, pushing Suffolk to reevaluate. Now it’s just 20% of revenue, with 36% from data centers and more than one-fourth from aviation and universities, including Dartmouth, Boston College and Northeastern.

In an industry that has been changing so much—for the first time in history, construction costs are higher than the value of some finished buildings, Fish says—he is even more open to new ideas. Every quarter, he invites a company from overseas to come to Boston to exchange ideas and learn from each other. Among recent visitors: Goldbeck GmbH, one of Germany’s biggest construction companies, known for its focus on efficiency and prefabricated building systems; and Kazakhstan’s BI Group Construction Holding, which claims to be the top development company in the Central Asian region.

Suffolk also sends teams overseas: a group recently spent time in Japan at Takenaka Corp., a more than 400-year-old firm. Some executives also traveled last year to a leadership retreat in Normandy, France, where they attended lectures from Harvard Business School professors and military personnel, and studied leadership case studies from the D-Day invasion.

Fish is convinced all of this will help his company survive this time of change.

“There is a reckoning right now in the industry,” says Fish. “We’re trying to lead the conversation both from an AI and need-to-digitalize standpoint. If you don’t go in this direction, you’ll perish in six to 12 months.”

Ankur Jain founded fintech firm Bilt Rewards in 2019, aiming to replicate the success that airlines like Delta have had with their rewards program—but targeted at apartment and home renters. Key to the company’s progress to date: inking deals with a range of crucial partners, from some of the country’s largest apartment building owners to credit card issuer Mastercard to merchants like Alaska Airlines and Lyft.

The beauty of this model is efficient customer acquisition.

“I learned the hard way on my first business that [the] model doesn't work at scale when you're just spending to acquire customers,”says Jain, referring to Humin, a contact management app that he cofounded in 2012.

(Dating app Tinder bought its technology four years later for an undisclosed sum.) These days he doesn’t have to spend much to acquire customers. His company gets paid by his real estate partners to handle tenants’ monthly rent payments. In return, renters who choose to join Bilt earn reward points to use at other merchants.

For Bilt, getting the first apartment owner to sign on as a partner was hard.

“It was two years of pitching,” recalls Jain, age 35. In the middle of the Covid pandemic, when apartment vacancies had risen in places like New York City, property owners became willing to take the risk of working with an unproven startup. In 2021, AvalonBay Communities (owner of 90,000 apartments in 12 states); Related Companies (owner of 73,000 apartments) and Equity Residential (owner of or investor in 84,000 apartments) agreed to bring on Bilt to handle its tenants’ payments.

Bilt later signed deals with outfits like fitness chain SoulCycle and other gyms, rideshare firm Lyft and more than 20,000 restaurants, enabling Bilt Rewards members to earn points each time they take a class, hail a Lyft or have a meal. Every time they do, Bilt gets a sliver of the revenue those members generate. Then Jain’s company passes a sliver of that back to the property owners (he won’t say how much).

Jain describes Bilt’s model as having a flywheel effect. “As we started getting the first buildings [signed] on and they had success, it then helped us attract more merchants, which then generated more revenue to share back with buildings who were part of the ecosystem, which then helped us sign more [apartment] buildings,” says Jain.

The company has 3.5 million customers and had revenue last year of $275 million, up from $116 million in 2022. Private investors have put more than $550 million into Bilt, valuing the company at $3.25 billion.

Robert Hale trained for and ran the Boston Marathon with 30 teammates last year. In August, he and 35 others will ride bikes 186 miles over two days from Sturbridge in western Massachusetts to Provincetown on Cape Cod as part of the Pan-Mass Challenge, an annual fundraising event for the Dana-Farber Cancer Institute. Most workdays, he also joins regulars at a CrossFit training class at 6:30 a.m. and again at noon. An exercise junkie? Maybe. But there is another reason for his fitness regimen: teambuilding.

The CEO of $1.8 billion (2024 revenue) Quincy, Massachusetts-based telecom firm Granite Communications describes these and other company activities, from 14 intramural sports teams and charity events to book clubs and game nights, as the “bedrock” of Granite.

“It matters to everyone to be a part of a community they care for,” says Hale, 58, who insists that keeping his 2,000 employees happy is key to the company’s success.

Before Granite, he started another telecom firm, Network Plus. Wooed by Wall Street, Hale took on debt and then took it public in 1999. But it struggled amid the dot-com bust and declared bankruptcy in 2002, laying off hundreds of workers. It had a big impact on him.

“I was focused on 90-day thresholds,” he says, not his team—and not on the long term. He hasn’t made that mistake again, choosing to keep Granite private so he could run it as he sees fit.

Beyond the perks are real benefits: Granite commits to almost exclusively promoting employees from within and gives managers a pool of money to dole out as promotions and raises. Granite employees, in turn, are the ones who keep its 17,000 customers, including 75% of America’s biggest companies (Nike and CVS, for instance), happy.

“There is a vigorous emphasis on making customers happy through thick and thin, and that in turn makes [staffers] happy,” says Hale. “Happy customers, happy teammates, full circle.”

Maybe it’s because Raj Sardana arrived in the U.S. from India with just $100 in his pocket. Or maybe it’s because the Georgia Tech graduate got laid off from his early job as an electrical engineer at a Pratt & Whitney supplier. Whatever the reason, Sardana is always obsessing over what his IT services provider, Innova Solutions, can do next for its customers.

“We’re paranoid. That’s why we work so hard,” says the self-made billionaire, who claims to still work 18 hours a day, seven days a week making sure Innova delivers more to its customers than it promises. “We’re client focused. We understand their pain points and solve them with technology,” adds Sardana, age 65.

Back when Innova’s predecessor, American CyberSystems, was getting started in the late 1990s, Sardana brought Indian programmers over on H1-B visas to help U.S. firms prepare for the Y2K “millennium bug.” That crisis ended quickly but then came the September 11th terrorist attacks. Leveraging his aerospace background, he began supplying much-needed engineering talent to defense contractors like Northrop Grumman.

Nowadays there’s a lot more competition in the world of outsourcing, and Innova gambled on acquisitions to keep pace, picking up attractive clients like Tesla and Harley Davidson. It bought six companies in 2021 and 2022, tripling its revenue to $2.4 billion. Innova hopes to win more business from existing customers.

“Marketing is not my strength. Instead I make sure we deliver excellence,” says Sardana. “If we acquire a client from [an] acquisition, we wow them with delivery.”

One Sardana says they wowed is a large North American bank, which Innova added to its client list as part of a 2021 acquisition; since then, the bank has increased its spending with Innova by 37% to $80 million annually.

Last year Innova’s revenue dipped to $2.3 billion as it jettisoned money-losing clients and focused on profitability, more than doubling its net profit margin to 6%, but it’s hoping for more wins ahead.

Innova is working quickly to incorporate generative AI to improve cost optimization. In one case, it is using AI on behalf of a telecom client to automate test cases, or essentially checklists that help make sure software is functioning properly; that in turn helped cut its quality engineering costs by 30% and reduced the number of Innova staffers needed for that client to 219 from 300. Says Sardana,“We always have to be on the cutting edge. We’re always looking ahead of the curve.”