I would make sure you can make money from photography before buying a D300...
Why? I love photography and I think I can really become even better at it with a D300.
Besides, I know for a fact I can sell photos I take at tournaments, I got so many requests to sell raw material at NPL1.
I don't know if I read it wrong, but buying specific photos online is never really the best idea. There are so many ways you can get pictures off the internet for free with the copy right.