I started when I was around 16. First, I built a website for an anti-drug agency in Romania. I remember that I used only HTML and CSS back then, and it was a real hassle. But everything worth doing it, because that's how I actually learn to code.
I was 10. Found a book at a garage sale on visual basic after I got my first PC and taught myself. First thing I ever remember building was just a red square that flashed on the screen and I was hooked. First software I ever sold was a hotel reservation system when I was 16.