If you decide to push mow your customers yard? Make sure you charge them for your time. I wouldn't use a trim mower (21 or 22") unless you have to bag some leaves or cant get into the back yard. If you have a walkbehing that should do fine. Explain to the customer that if they insist you to push mow the price will be that much more than if you used your rider. Just figure out how long it will take you to push compared to riding. I use a formula of what I am worth a hour, times how many times I will be on there property a year, and divide that by 12. Hope that helps you out a little? Stefan