11 for me. My son started when he was 9 (he is almost 12 now). I had to hide my 1st edition AD&D books under the matress (stupid media) - he's got someone that drives him to the local hobby shop.
I was either 13 or 14, so it's been 13-14 years since I first started. It's frightening to think about all the time and money I've spent on this hobby. Especially when I realize that I still spend a ton of cash and I don't really get to play that much anymore.