We all know that some entrepreneurs get rich quick, but still others do it even while they're young. Quite a few of them are making their first million before they're even of legal drinking age.

While most teens spend their youth honing work skills in entry-level jobs, whether that's slinging fast food or working retail, others get that spark to succeed at an early age. There's no shortage of useful advice out there to help even the very young make strong business decisions. There is also no minimum age to become a millionaire, as these "kids" know firsthand. From playing the stock market to starting up their own companies, check out these 40 teens who made millions before turning 20.

1. Ashley Qualls: The founder of WhateverLife.com got her ingenious idea back in 2004 when she was just 14. Meant to showcase her design skills, the site really took off when Qualls started doling out freebie MySpace layouts. An anonymous buyer offered her $1.5 million and the car of her choice, but she declined.

2. Juliath Brindak: She began creating sketched characters at age 10, and then developed a complementary social-media platform at 16. Her Miss O & Friends company is now worth an estimated $15 million, though Brindak gets most of her revenue from ads.

3. Sean Belnik: With just $600, Belnik started an e-tail shop at 16, beginning with small items such as trading cards. He then moved on to furniture, founding BizChair.com and proving a knack for the market. By the time he was 20, he was worth $24 million.

4. Adam Horowitz: When he was just 15, Horowitz challenged himself to make his first million by his 21st birthday. He's the developer of Mobile Monopoly, which is a tutorial for learning mobile marketing. He reached his goal and earns an anonymous "six-figure income."

5. John Koon: Koon was only 16 when he kickstarted New York City's inaugural auto parts business, Extreme Performance Motorsports. He scored a deal with MTV to provide products for reality shows, and then used his connection to team up with Young Jeezy for a fashion line. He's already worth $40 million and by all estimates will soon be a billionaire.

6. Cameron Johnson: By the time he was 11, Johnson's knack for creating greeting cards had earned him thousands and leverage to start his own business. SurfingPrizes.com was his investment strategy, which is a toolbar service that rakes in about $350,000 per month. When he was a high school senior, he was worth at least one million.

7. David and Catherine Cook: This brother and sister team got rich by creating MyYearbook.com, which remains a player in the social-media realm. Their older brother invested $250,000 in their digital yearbook idea, and today the site is worth about $100 million.

8. Nick D'Aloisio: At 17, this entrepreneur had designed an app worth $30 million according to Yahoo. He started coding at 12, which led to the development of a news app. He credits an eye for spotting market disparities as his catalyst.

9. Tyler Dikman: By eighth grade, Dikman was charging $15 an hour to fix computers. His skills caught the eye of Merrill Lynch executives, and he was hired by Malcolm Taaffe at age 15. He soon started his own business, Cooltronics, repairing computers--making millions and scoring him a spot on Businessweek's 25 Under 25 list.

10. Fraser Doherty: Only 14 when this Scottish entrepreneur began making homemade jams via his grandmother's recipe, his SuperJam business was booming by the time he turned 16. When a major U.K. supermarket asked to stock his products, he took out a $9,000 loan and became a millionaire. His recipe books can be found on Amazon.

11. Captain Sparklez: This pro gamer began his career by posting how-to videos on YouTube, and then he expanded into a channel offering detailed gaming instruction. One of the highest earning YouTubers today, he's worth more than $8 million.

12. Mark Zuckerberg: Many people forget that when Facebook's founder started swimming in wealth, he was a young college student. Almost everyone knows the story of Facebook, and Zuckerberg's now one of the wealthiest people in the world, at around $20 billion, regardless of age.

13. Michael Dunlop: He dropped out of high school after his dyslexia had teachers telling him he'd never be successful. He founded IncomeDiary.com, which today boasts a 12,000 rating on Alexa and earns him a hefty six-figure income. While his blogs aren't flawless grammatically, his business advice is spot on.

14. Andrew Fashion: Not all teenage millionaire stories have happy endings. Fashion designed mini rocket launchers and was worth more than $2 million by the time he was 20. He then blew it all on women and gambling by the time he turned 22.

15. John Magennis: Starting a Web design business at 14, Magennis is totally self-taught. Initially he charged just $15 per site, but today he can demand upwards of $30,000 per site. He earned his first million by his 16th birthday.

16. Tim Sykes: The famous and young stock investor used his bar mitzvah cash for his first investment. He started with penny stocks and was worth more than $1.5 million by his 21st birthday. Today he's also an inspirational speaker and teaches others how to get rich with penny trading.

17. Maddie Bradshaw: Featured on Shark Tank, Bradshaw (along with her younger sister and mom) started by designing locker decorations using soda bottle tops because she couldn't find anything similar she liked on the market. She earned $1.6 million in her first year, and by the time she was 16 she had lured an astonishing three "sharks" as investors and partners.

18. Kiowa Kavovit: The youngest entrepreneur on Shark Tank to date, she was just 6 years old when she pitched Boo Boo Goo to the sharks. Scoring a $100,000 investment, this tiny and newly minted (in 2014) millionaire slings a paint-on bandage designed for kids--of course.

19. Diane Keng: This 18-year-old entrepreneur is working on her third business, but she first hit paydirt with MyWEBoo, which helps teens manage their online reputations. She's also founded a T-shirt company and a business that helps companies market to teens.

20. Chris Phillips: Phillips at 17 was already the founder of Dot5Hosting, making his first million by providing Web hosting and domain name registration. At 19, the British techie was making $10 million every single year with no sign of slowing down.

21. Farrah Gray: What started as a gig selling body lotion at age 6 became founding a business at the age of 13. Gray is the owner of Farr-Out Food, which raked in orders worth $1.5 million by the time he turned 14.

22. Brian Wong: In charge of Digg's business development strategy at just 19 years old, Wong has since headed up Kiip--a leading mobile rewards company. Already he's earned $15 million in a capital investment campaign alone for Kiip, which is said to be a game changer.

23. Madison Robinson: A 15-year-old Robinson created Fish Flops, originally only selling flip-flops with teen-centric designs. She soon branched out to include other apparel and even a complementary app. Earning $1 million in sales before she could drive, she epitomizes entrepreneur.

24. Justin Bieber: The only celebrity to grace this list, Bieber's success is worth noting because of his humble YouTube beginnings. Although media coverage suggests otherwise, he's actually proved himself to be a pretty savvy entrepreneur, branching out into apparel, fragrance, and the like to capitalize on his A-list status.

25. Elise MacMillan: She had teamed up with her grandmother to make candy ever since she was a toddler. At 11, she worked with her brother in a commercial chocolatier and founded the Chocolate Farm. She earned top spots on lists by Ernst & Young and several other accolades.

26. Athina Onassis Roussel: While there are many millionaire heirs and heiresses in the world, Roussel is worth noting because she's one of the richest, and comes from a particularly well-known lineage. She is the only surviving descendant of Aristotle Onassis, who was once famously married to Jacqueline Kennedy Onassis.

27. Robert Nay: A self-taught coder, when Nay was just 14 he drummed up 4,000 lines of code to create the Bubble Ball game. He made it free to download on Apple, and in two weeks more than one million people had downloaded it. He earned $2 million in those two weeks.

28. Julianne Goldmark and Emily Matson: This duo created hair ties, getting inspiration in the eighth grade when they envied celebrity high-end ties but couldn't afford them. By their senior year of high school, the friends had cashed in on a connection one of their moms' had to Jennifer Aniston, and they now make about $10 million per year.

29. Connor Zwick: He started toying with Javascript in middle school, and by 19 was making some of the most in-demand tutorials in the industry. The builder of the Flashcards+ app, Zwick eventually dropped out of Harvard to study under PayPal's founder.

30. Scott and Stacey Ferreira: The brother-sister duo launched MySocialCloud.com when Scott was in college and Stacey was still in high school. However, their entrepreneurial spirit was sparked as young children watching their father work at IBM and Google. A $1 million investment for the cloud-driven social-media platform has already been secured.

31. Dominic McVey: When this Londoner was 13, he started importing scooters from the U.S. (which were much cheaper than what was domestically available, given the dollar to pound ratio) and selling them locally. He was a millionaire by the time he turned 15. McVey happened into a partnership with Viza when he was Googling "Visa" and now is worth around $10 million.

32. Gary Martin: This Irish early entrepreneur began running his own nightclub at the tender age of 15 (the drinking ages in the U.K. are vastly lower than in the U.S.). By the time he was 17, he had moved on to property management. By 18, he was worth $20 million and counting.

33. Michael Furdyk: He founded TakingITGlobal at 17, and now Furdyk spends his time growing his business in more than 200 countries. He's also a public speaker, a consultant, and a regular guest on some of the most popular talk shows in the country.

34. Abbey Fleck: The inventor of Makin' Bacon designed the first microwave bacon cooking technology when she was just 8. A favorite on the infomercial circuit, she's been featured on numerous talk shows.

35. Mike McDonald: This Canadian with a knack for gambling started toying with online poker at the age of 15. He was feeling pressured to get a job by his parents, but he didn't want to do the usual teen gig. He was a millionaire as a teen and today is worth more than $5 million.

36. Carl Churchill: The British entrepreneur started his first Web design business at age 12. Today he's worth around $10 million, but he made his first at 19. Dubbed the British Bill Gates, he's also a philanthropist and venture capitalist.

37. Andrew Gower: Another teen millionaire from across the pond, Gower is a game developer and the founder of Jagex Game Studio. He started developing at age 8. Now the 46th richest entrepreneur in the U.K. and worth almost $200 million, he made his first windfall as a teen.

38. Patrick Collison: An Irish teen millionaire, Collison began winning numerous young scientist prizes at age 14. He founded Shuppa with his brother, moved to California, and made his first million by the time he was 19--bringing his brother along for the lucrative ride.

39. James Murray Wells: When the young college student in Britain realized there wasn't an online e-tailer for eyeglasses, he quickly filled that need. Using his student loans as capital, he earned $4 million his first year in what he called a "recession-proof business."

40. Matt Wegrynz: Buying and selling domain names is what made this entrepreneur so wealthy. He started at 17, with some of his best deals going for six figures.