I cut my own 4 acres
with my Exmark Quest 48", 23hp B&S ELS in about 2.5 hours. It cuts beautifully. I've cut some really tough grass (thick field grass 18" high) and it handled it with two passes. Given the number of times I cut a year, I have a hard time topping 50 hours a year on the machine. It comes with a three year warranty. Do the math in your situation and you might not need a commercial machine. It cost $4300 after tax.