That Deere looks a bit too light duty for commercial cutting. I think you need to step it up a notch or risk buying a disposable mower. Gravely's HD series mowers look decent as does the Exmark Pioneer (looked at one yesterday in fact). I see some commercial cutters around me using the Scag Freedom mowers.
Bob-Cat has some reasonably priced machines too...the Fastcat Pro prices are pretty good.