Actually you would be better off charging by the cut than trying to achieve an hourly rate. If you are a collage kid hoping to pick up a few extra yards this summer to make some extra money you can't compete against a Professional Lawn Maintenance crew that's doing it for a living especially if you are a solo operator. The Lawn maintenance guys are going to be faster and have the equipment, ZTR's Trimmers, Hedge trimmers, pole saws edgers, anything they need and two or three of each to do the job that needs to be done or that the client wants done. If I were you I'd find a Sub-division with small lawns that you can cut,trim, edge and blow off in 30 minutes, charge $17.50 to $20.00 a cut, two in an hour and you can get you into your 30 to 50 an hour.