I'm 13 and I really want to start my own business. I love photography so I thought that might be a good route to go down. I need to know:

What kind of picture sells best? Do people want landscapes, arty type things, plants, etc?
How much would I be looking at to get say 20 canvas prints? Or is there a different type that would be cheaper?
As a second part to that question, who much would I be looking at to sell a medium sized picture at?
Is 13 too young? Would people take me seriously?

Here is my Flickr page with some of my favourite pictures, most of them taken on a trip to Whitby (UK)

http://www.flickr.com/photos/sparky_images/

Thank you in advance!