Sounds great

Just because you are writing a story about horses doesn't make it fanfic. As this story isn't going to be in the Black Beauty universe and Black Beauty isn't going to be making any appearances, then you should take this down, and when you start posting the chapters of your actual story, post them in ine origional fiction section of this site.

Very intersting. I like the commercial idea. It makes me want to read more, badly... So, hurry and write!