I think the decision to rent or not will depend on demand. In my opinion you have to identify your target market. Grass cutters will look for rental equipment only when their equipment is down or stolen. Short term rentals I would imagine. It would not be cost effective for a company to rent long term. Do the mower shops in your area stay behind on service? Is there another company in your market currently renting? Do you have enough equipment to support your own operation when you are renting, or are you looking to stop service and strictly rent? Who is responsible for service and repairs?
It is an interesting concept... let us know how it goes!