It's a classic business story: An entrepreneur comes up with a brilliant idea, pitches it to deep-pocketed investors and builds a billion-dollar company seemingly overnight. But not every successful business has gone that route. Many well-known brands started out growing slowly and methodically on their founders' own dime. Then they grow as founders sink internal cash flow to fund company development. Here are five that show good businesses can thrive even without a boost from the venture capital world.

Sara Blakely first came up with her now-famous women's undergarment when she was getting dressed for a party. Unable to find a form-fitting piece to wear under her white slacks, she decided to cut off the feet of her control top pantyhose. At 27, Blakely launched her Atlanta-based business using all $5,000 of her personal savings. She even wrote a patent application and filed it herself to save on legal fees. To date she still owns 100 percent of Spanx, which had an estimated $400 million in 2016 sales, and hasn't taken a penny from outside investors.

When Nick Woodman's entertainment and promotions website FunBug went bust in 2001, he decided to clear his head with a surfing trip to Australia and Indonesia. Inspiration struck when he noticed that the cameras surfers were wrapping around their wrists to photograph their adventures kept breaking loose. Using his personal savings and a $35,000 loan from his mother, Woodman launched GoPro (originally known as Woodman Labs) in 2002. He bootstrapped the San Mateo, California-based business until 2012, when tech manufacturer Foxconn invested $200 million. Two years later GoPro went public at a $2.96 billion valuation, according to Bloomberg.

Craig Newmark started his eponymous classified ad site in 1995 as an email newsletter to keep friends updated on interesting events around San Francisco. As word spread, people started asking him to post jobs and list items for sale. Craigslist hit a million page views per month by 1997, but Newmark kept it as a side project and didn't incorporate until two years later. He didn't take any outside money until 2004, when eBay paid $32 million for a 28 percent stake in the company. After a lengthy lawsuit in which Craigslist was accused of diluting eBay's financial stake, however, Newmark bought back the shares. In 2016, Craigslist topped $690 million in revenue, according to AIM Group.

Founded by Tom Preston-Werner, Chris Wanstrath, and PJ Hyett in 2008, GitHub (a 2017 CNBC Disruptor 50 company) is a software development platform where users can share their work on projects with others. According to Preston-Werner, the founders spent only a few thousand dollars to set it up the company, and it became profitable "the day we opened and started charging for subscriptions." In the early days, San Francisco-based GitHub didn't have offices. Instead, the four full-time team members worked remotely and used coffee shops to meet a couple of times a week. Four years later the company first sought funding, landing a $100 investment from Andreessen Horowitz. Since then, GitHub has raised more than $250 million from other investors; a 2015 funding round valued the company at $2 billion.

In 2010 co-founders Will Dean and Guy Livingstone tapped into a rich market with its series of edgy athletic competitions. The idea the pair devised is a boot camp–style footrace that features obstacles such as barbed wire and butter-greased monkey bars. They spent $300 on a website and about $8,000 — all the money from Dean's bank account — on Facebook ads to promote it. The strategy paid off: More than 5,000 people ran the first Tough Mudder, and more than 2 million people have run the company's races in 10 countries since. The Brooklyn, New York-based company generated more than $100 million in revenue through registration fees and sponsorship deals in 2015 and still has not received any outside investment.