Comment by mikeyur

12: Started selling pirated software and DVDs to classmates.

13: Illegal firecrackers to friends in high school (they're illegal where I live in Canada)

14: First internet venture - started a hosting company with a good friend of mine

15: Sold my first blog (Mac-software blog) and was hired to start another by a blog network

16: Started affiliate marketing with the SEO knowledge I gained at the blog

17: Hired by a local startup as their marketing manager

18: Started working fulltime as an internet marketing consultant

Turn 20 in a week. Not really sure if any of them would count as a startup.