My fee varies based on how much work I feel your story needs and how much you want to polish it. Writers vary in their skill levels.
For this reason, I do not have one rate that fits all writers.
You can start by presenting a small sample with a modest introductory fee. My feedback on your sample will show what I can do for you.
With my feedback, I will tell you my rate for further work. Even if you decide not to continue working with me, you will have received the benefit of a detailed critique for a very modest introductory fee.
You are in the driver's seat on this. See:
How to Get Started with a Novel or
How to Get Started with a Memoir or Biography.