I think you have come up with the best idea. But I'll bet she says "what are you sure, why didn't you let me know before, I was not happy with your work. I've has people do that to me in the past. I just make sure I get CASH before services rendered and take a picture after each mowing/trim or she will have you redoing things because she will find something wrong so you have to come back in 4 or 5 days after the work has been done. And stick to your word, to you and her. "But thats just me" Good Luck and keep us posted.