kitten val: I definitely want to make things worth her money, which is why I'm kinda struggling with the price. Now I'm thinking $400/month however I don't have an indoor arena....so my work with the horse is dictated by the weather. But like I said, the owner knows this. I don't want to under-charge (for my own benefit) however I really don't want to over-charge her, I want everything to be just right. I'm not sure what the going rate is around here for training other than that one barn I mentioned earlier.
As for weather, Sep and Oct are usually the best months to ride, so I'm sure that won't be a problem.
P.S. After reading iride's response I think he gave a great idea. Taking lessons with you during training would be a great benefit to both of them (horse and rider), and it would build those extra money as well.