The only differences between the IS500Z and the IS1500Z are deck and engine choices. Do you really need an engine rated for 2000 hours to mow a couple of acres and put on perhaps 100 hours per year? Routine maintenance on any engine can go a long way to preserving its life. I have a collection of old 2T Lawnboys that have been cutting grass for 30 years or more. I am sure none of them would be considered 'commercial' grade what ever that actually means. If commercial grade means used by commercial cutters a Walmart special thrown into the back of a rusting Ford pickup is commercial grade.
Scag Tiger Cat 48-inch deck, Kawasaki motor
Lawnboy 10227 2T push mower
Stihl BG86 handheld blower
Stihl BR550 backpack blower
Stihl KM110R kombi system with lots of attachments
Stihl HS45 hedge trimmer 24-inch blades
Echo SRM210 trimmer