Hi i like to take portraits and would like to move in to do portrait photography for business. I'm still working on my skills and thus currently not doing any sort of business. However I'm really thinking of heading in this portrait business direction. I'm thinking of upgrading my camera to Nikon D90. Is this camera good enough to go and do business with it or it's better for me to save and get the D300. I was also told that one reason why D300 would be better is because i can use it to substantiate the rate I'm charging.