However, consider this... you son is interested in Photography. That is great because there are a lot worse things he could be interested in. Obviously, you are a good role model for your son.
Please don't take this as rude but... stop asking us know-it-alls and just go and buy him a camera already! Furthermore, price be damned! So what if you save a few or lose a few dollars. It's your son, not the next door neighbor's son!
Make it a big deal, you know... a camera case, batteries, filters, and other accessories. Perhaps a book or two - be sure to write an inspiring message in the book. If you're on a budget, give him a lessor model but still do the rest.
I guaranty that your son will *always* remember the moment when you give him this gift!
Now go do it now before he discovers rock and roll, sex, and drugs.
Okay, that was just my humble opinion!