1) I was dragged into it - I was 12 years old and a member of a forum that was shutting down. My limited experience in HTML + CSS and a bit of naivety made me think I was an expert in web development, so I offered to take over. I basically had to learn PHP + MySQL overnight and over the course of my 2 month summer I spent late nights reading code to try and figure out what it did (i.e. no books, just trial and error and a lot of Google).
2) Started around the time I turned 12 years old, so June 2006.
3) I started making money in varying ways almost right away. I took over the site and installed Google ads within a few months. I probably started doing freelance within a year. My first full-time job was this past April doing an internship after first year university.