Your Side Hustle Can Become a Million-Dollar Business. These 5 Examples Prove It. Under Armour evolved from its founder's wish for a moisture-wicking t-shirt. What's your pain point and future million-dollar idea?

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Under Armour

Do you currently have a side hustle? A secondary stream of income? A hobby you enjoy that can sometimes make money?

According to CNN, more than 44 million Americans have at least one side hustle, but if you're like the vast majority of them, you haven't considered the thought of expanding yours into a full-time business. You might think it lacks the potential, or that you don't have enough time to expand it; but the reality is, almost any profitable side hustle you have could feasibly turn into a much bigger, money-making enterprise.

Still skeptical? Take a look at these examples of entrepreneurs whose side projects were supposed to remain "just" side projects, but ended up becoming massive successes:

Related: One Thing Coca-Cola, Geico and Under Armour Are Doing That Every Company Should Do Today

1. Under Armour

If you haven't heard the Under Armour story before, you might be surprised to learn that Kevin Plank, the company's original founder, didn't start out with dreams of starting an internationally successful company. Inspired by the discomfort of his own sweat-soaked T-shirts, Plank designed a t-shirt with moisture-wicking fiber, and started production in his grandmother's basement.

Before landing his first team deal, he was selling those shirts out of the trunk of his car. Under Armour now makes billions in revenue each year.

2. Chipotle Mexican Grill

Chances are, you've had one of Chipotle Mexican Grill's massive, foil-wrapped burritos. Whether you're a diehard fan who eats there regularly or you tried it once based on a friend's recommendation, there's no denying that the company's healthy basic menu has made an impact on our culinary world.

What you may not know is that the chain started out as a small side business, opened by founder Steve Ells in 1993. Ells took out an $85,000 loan, hoping to sell just 107 burritos a day to break a profit. By the end of the month, however,he was selling over 1,000 burritos a day, reinvesting the money into the business and eventually expanding to more than 2,000 restaurants nationwide.

3. Etsy

Accounts of the story behind the motivation and execution of Etsy aren't consistent. The details vary depending on whom you ask, but one thing is clear: Etsy was never intended to be the massive marketplace it turned into. According to interviews co-founder Rob Kalin has given, the idea sprang from his desire to sell his own craft -- wood-encased computers -- and his distaste for current online marketplaces, like eBay.

Related: 21 Strategies for Providing Top-Notch Customer Service on Etsy

According to one of Etsy's product managers, Etsy emerged out of a side hobby of freelance website-building. Whatever humble beginnings it did actually have, Etsy has become a force to be reckoned with on the national scene. A one-time simple solution for a common problem its founders responded to has evolved into a household name in the world of artistry and crafting.

4. Craigslist

Craigslist is one of the least surprising entries on this list. With its minimalist design and practical functionality, Craigslist today still looks like somebody's side project. But in fact, the site dates back to 1995. That year, founder Craig Newmark started sending out a short email newsletter to a dozen of his friends, noting some of the local events happening around San Francisco.

After those newsletters became a regular occurrence, more people started requesting to be added to the CC list. Eventually, the audience grew larger, the requirements grew more intense and Newmark started automating the email blasts. Pretty soon, his "side hustle" was too much to manage, so Newmark built Craigslist, and by the end of the 1997, the site had hit a million page views per month.

Craigslist remains one of the most frequented classified listings on the web, despite staying true to its simplistic format.

5. Yankee Candle

Yankee Candle has a sweet origin story; the company's founder, Michael J. Kittredge, wanted to get his mother something for her birthday. Not having much money (he was only 16 years old at the time), Kittredge decided to make her something.

He melted down a couple of crayons, added other household ingredients and made a candle. After his neighbor offered to buy a candle for $2, Kittredge started experimenting with candle design, and eventually built an empire that expanded to more than 575 retail stores and 35,000 authorized retailers around the world.

The company now produces more than 200 million candles every year, and in 2015 reached $1 billion in sales.

Hopefully, Kitrredge's story inspires you to consider taking your own side project to the next level, or at least acknowledge the possibility that entrepreneurial success can come from humble beginnings.

Related: For American Franchisors to Succeed Overseas, They Have to Be Open to Change

You don't have to turn your side hustle into a billion-dollar enterprise to be successful. But knowing the possibilities -- which these stories illustrate -- can help you set higher goals, and motivate you to push yourself to achieve whatever you want to, in whatever direction you choose.

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