I started cooking from day 1 after i got kicked out of the house and got my own place. I was 19 at the time i guess and i was still simple minded, just getting mostly pre-made stuff that I only needed to reheat. Over the years I started watching a few shows, looking over the internet for new recipes and thinking that I can do better then store bought stuff. I started trying to reverse engineer certain things. Eventually @DinohScene came along and i fed him my still incompetent undercooked potatoes. I started getting a drive after that, that I wanted my food to be able to compete with restaurant grade food. So I kept on practicing.
Just after Dinoh and I started living together I even managed to get a hold of a job as cook. Not fastfood or w/e, real cooking as in entire dishes. Couldn't handle the stress of the job unfortunately, but I never had a single dish send back to me. As of now, I still try to experiment with different things like my suprise buns that I made recently. Dinoh is a perfect guinea pig for testing my foods. c:
I guess from the age I was about 13 or 14, I cooked dinner one day of the week (not all by myself though) and that went on for a while.
I did some cooking in school before that though.
Moved out at 16, and did a lot of cooking at that time, making heavy use of the recipe leaflets that were at the grocery store, picking whatever sounded good. Shame they got rid of those as they made it much easier to cook varied dishes. Nowadays I just stick to the same few dishes and rarely ever made from scratch. Looking online for recipes is effort especially when I don't know what I want and most of it doesn't particularly interest me (if I am going to go out of my way to cook from scratch then it better be one of the most delicious meals I have ever had)
I think somewhere around 7-8 years old if you count making sandwiches in. As for proper meal-like think, maybe 10 years old. And only because earlier I was too dumb to use a stove.. and too short to reach most shelves.