Buy the best commercial equipment. I always buy new mowers, and blowers. You can pick up some good used weed wackers. A Used mower or blower is not a smart idea. You don't know if they changed the oil regularly on that used mower (maint. tracking). Blowers can get beat to hell especially during cleanup times.
I say pay more for the quality and reliability a new mower and blower provide. Don't go cheap on your tools. If this is your business invest in it and it will pay you back.