As a Beta Reader, here's what I have to offer:
* I'll look at a sample of your work to see if we're compatible. I don't want to waste your time.
* Read your story from the perspective of a reader, not an editor. I'm not looking for grammatical errors or typos. But if a significant number of issues are found, and they interrupt the flow of the story, I'll bring them to your attention.
* Offer constructive criticism regarding character and story arcs, dialogue, pacing, and plot inconsistencies.
* Suggest ideas on how to improve your story.
* Provide you a written report.