$50 per hour minimum plus materials. It wouldn't be a bad idea to have a customer sign a waiver before performing any wetsanding to protect yourself in case of problems down the road. Factory paint jobs are not meant to be wet sanded contrary to common belief. Removing any significant amount of clear (over .3 - .5 mils) will eventually lead to premature clearcoat failure. Refinish paint jobs are a different story as they usually have additional clearcoat to provide for sanding and polishing after the repairs and repainting are done. My best advice is use your ETG guage to check the paint thickness before, during and after you wetsand so you know how much material you are taking off. Good luck.
I call the local mobile chip repair/ dent repair guy. He reimburses me 25% of his fee so I don't lose out on subcontracting the business. But I just really hate doing wet sanding work.