CAUT

An adjunct piano professor at my school is learning to tune pianos. He's helped me a few times with some repairs, for which I've paid him out of my own pocket. (getting reimbursed by the school). But we've just set him up to be paid directly by the school. It's kind of complicated because the school has limits on how much he can make as a contract employee while still teaching. 

As I said, he's taking the Buttler school and his tunings are OK, but for now he's mostly doing minor repairs and regulations, and occasionally a touch up tuning. The question I have is, how much should he be paid to do this? Either by the job or per hour.  What are some of you paying?