I think just the fact that you are reaching out is a good thing. A lot of people I have seen start agencies just figure they have been a photographer and have shot image, so they can make an agency. This is far from the "normal" truth.

As far as pricing, I think traffic is the most important thing. If you are going to start out you HAVE to be cheaper than the Dreamstimes and iStockPhotos, because it is probably the only way to steal their customers. Once you have a couple million images and a good client base you can play with prices again and start moving them up. Dreamstime dealt with this differently, by letting the images slide up a "Image Level" scale. I think that is nice because it appeals to the customer and the photographer.