Looking to take over a service business from current owner.
He will help maintain machinery and teach me as needed. I have worked with him for several years, the business can be very profitable.
He needs to do less physical and more mental/office end of the business.
He is asking for 18% off the top of every job from current customer base in the future. (Most jobs run at less than 20% cost for materials and overhead, so I could still pocket 60% after paying him and materials.)

Plan is for 5 years, I pay him 18% of repeated business, anything I find on my own, he gets nothing.

Does this sound reasonable/comparable to any situations you may have heard?

Seems high to me, but also great opportunity to make more than I currently do, and if I can bring in more work, what is there to loose, right?