The global side hustle economy was valued at $556.7 billion in 2024, and in 2024, 36% of American adults have a side hustle, with an average of $891 a month in earnings, a 10% increase from 2023 to 2024. These numbers tell a clear story, really. People everywhere are hustling for extra income. Most of them will pull in a few hundred bucks a month. Some will hit four figures.
Yet once in a while, someone’s weekend project explodes into something far bigger than they ever imagined. We’re talking about the kind of success where a simple idea, started on the side while working a full-time job, becomes a company worth billions. These stories aren’t just inspiring, they’re proof that massive success doesn’t always require venture capital or a fancy business school degree from day one.
What these founders did have was persistence, a willingness to fail, and the ability to spot an opportunity others missed. Let’s look at some of the most remarkable transformations from side hustle to billion-dollar empire.
Instagram Started as a Whiskey Check-In App
Originally created as “Burbn,” a location-based check-in app, Instagram’s transformation into the photo-sharing giant we know today was no accident. Kevin Systrom and Mike Krieger weren’t trying to build a photo app initially. They were working on something completely different. They scrapped Burbn and started over. It seems obvious in retrospect, but it wasn’t clear at the time that this the was right move. The photography category seemed saturated, but Systrom saw an opening that many others didn’t.
The pivot happened fast. After months of testing, Instagram launched on Oct. 06, 2010. Systrom and Krieger didn’t know exactly what to expect, but 25,000 users showed up on the first day. For late 2010 when there were fewer iPhones on the market, that was a big number. Their timing was perfect because the iPhone 4 had just arrived with a camera good enough to replace point-and-shoot devices.
Growth accelerated from there. Instagram hit one million users in three months. Then that became two million, which then became 10 million users. In April 2012, Facebook announces that it has agreed to purchase Instagram for $1 billion in cash and stock. Instagram’s current estimated valuation of $200 billion means Facebook’s investment has multiplied 200 times, making every other billion-dollar deal in Silicon Valley history look conservative by comparison.
Spanx Grew From Cutting Up Pantyhose
Sara Blakely wasn’t an entrepreneur. She was selling fax machines door to door. After failing the LSAT twice, self-made billionaire Sara Blakely sold fax machines door-to-door for seven years. Then she had an idea that seemed almost embarrassingly simple. In the hopes of looking better in my fitted white pants, I cut the feet out of a pair of pantyhose and substituted them for my underwear. This allowed me to benefit from the slimming effects of the pantyhose’s ‘control top’ while allowing my feet to go bare in my cute sandals. The moment I saw how good my butt looked, I was like, ‘Thank you, God, this is my opportunity!’
With $5,000 Blakely had saved selling fax machines door to door, and no background in design, business or manufacturing, she launched Spanx in 1998. She kept it secret for a year, working on it nights and weekends. When she first started Spanx, she deliberately kept her idea hidden – even from her closest friends and family. Ideas are the most vulnerable in the moment you have them. I waited a year before I told any friends or family what I was working on and that’s because I didn’t want ego to have to get involved too early.
The hustle was real. Spanx was profitable in it’s first year of business with total revenue of $4,000,000. Oprah helped catapult the brand when she named it a favorite product. Blackstone bought the majority stake in Spanx, valuing it at $1.2 billion, and She grew Spanx over the course of two decades into a brand found in clothing stores around the globe and notably never took any outside investors. When she finally decided to sell in 2021, she reaped the entire $1.2 billion reward – a 240,000x growth on her initial $5,000 investment.
Craigslist Began as an Email List to Friends
Craig Newmark wasn’t trying to build a business empire. Having observed people helping one another in friendly, social, and trusting communal ways on the Internet via the WELL, MindVox and Usenet, and feeling isolated as a relative newcomer to San Francisco, Craigslist founder Craig Newmark decided to create something similar for local events. In early 1995, he began an email distribution list to friends. Most of the early postings were submitted by Newmark and were notices of social events of interest to software and Internet developers living and working in the San Francisco Bay Area.
What started as sharing local events snowballed. Community members started asking for a web interface. Newmark registered “craigslist.org”, and the website went live in 1996. Craigslist was incorporated as a private for-profit company in 1999. Around the time of these events, Newmark realized the site was growing so fast that he could stop working as a software engineer and devote his full attention to running Craigslist.
The business model remained intentionally simple. The ideal was first initiated as just a “side-gig” that eventually flourished into a $3 Billion company. Although Craigslist is considered a non-profit organization, the company had registered itself as a profit organization in 1999. Given that Craigslist remains to be a private company, its valuation is not disclosed to the public. With estimated annual revenues of 660 million, its valuation probably ranges anywhere between $2 billion to $3 billion. Craigslist proved you don’t need to monetize everything to build massive value.
WhatsApp Started with a Simple Messaging Idea
Brian Acton and Jan Koum weren’t Silicon Valley darlings. Acton had actually applied to work at Facebook and Twitter and got rejected by both. They started WhatsApp as a lean operation focused on doing one thing exceptionally well: messaging without ads or gimmicks. The app stayed subscription-based at just 99 cents per year after the first year free.
Growth came through word of mouth. The simplicity attracted users tired of complicated social networks and intrusive advertising. By early 2014, WhatsApp had roughly 450 million monthly users. Facebook saw the potential and made an offer that stunned the tech world: 19 billion dollars in cash and stock. It was one of the largest tech acquisitions ever at the time.
The founders had built something worth billions by focusing relentlessly on user experience and privacy. They proved that staying small, staying focused, and resisting the pressure to monetize aggressively could lead to a massive payday.
Shopify Began Selling Snowboards Online
Tobias Lütke didn’t set out to build an e-commerce empire. He wanted to sell snowboards online. The problem was that existing e-commerce platforms in 2004 were terrible. So he built his own using Ruby on Rails. The snowboard store didn’t take off, yet other people kept asking to use his platform.
That’s when Lütke realized he’d built something more valuable than a snowboard shop. He pivoted to offering Shopify as a service. The company grew slowly at first, focusing on small merchants who couldn’t afford expensive enterprise solutions. They went public in 2015 and kept growing.
Today, Shopify powers millions of online stores and has a market valuation that has reached well over 100 billion dollars at various points. Lütke’s side project to sell snowboards became the infrastructure powering a significant chunk of global e-commerce. His story shows that sometimes the tools you build to solve your own problem turn out to be the real product.
What These Stories Teach Us About Starting Small
Here’s the thing about these billion-dollar side hustles. None of them started with the goal of becoming billion-dollar businesses. Instagram was a pivot from a failed check-in app. Spanx was cut-up pantyhose. Craigslist was an email list. Mailchimp was a tool for web design clients. They all started small, solving real problems.
The founders kept their day jobs initially because they needed the income and health insurance. They worked nights and weekends. They dealt with skepticism from friends and family. Although there’s a flood of stories about individuals earning astronomical sums from side hustles, such instances are exceedingly rare. Usually, progress is slower than anticipated, resembling a dance of ‘two steps forward, one step back.
What separated these success stories from the thousands of side hustles that stayed side hustles? Persistence matters. So does timing. And recognizing when something has genuine traction versus just being a hobby. In March 2025, the U.S. saw 452,255 new business applications, a 6.4% increase compared to the previous month. With 55% of full-time workers interested in turning their hobby into a business, this surge could reflect the growing trend of individuals turning their side hustles into formal businesses.
The most successful founders stayed focused on solving problems rather than chasing valuations. They listened to users. They iterated constantly. They didn’t try to be everything to everyone. And when the right opportunity came along, whether that was selling or scaling, they had built something valuable enough to have options. That’s the real dream, honestly.
