My advice would be to take your time and look around at whatever is available (new and used) at a good value. And when I say a "good value" I don't necessarily mean the cheapest.....or the most expensive. I mean what ever you happen up on that provides you with the best machine at the best price.
And remember, negotiate
! Most dealers (and individual sellers) will add a little "wiggle room" in the price so they can come down a little, making the customer think they're getting a better deal. If a customer comes along and doesn't negotiate...the more "gravy" for the seller!
As several have said here, look at CL, eBay, and local newspapers. You may find a great deal by checking CL for surrounding cities...not just yours. By looking at all commercial mowers for sale, whether new or used, you'll find a much better value mower (because of a much larger group to consider) than looking for a particular name brand.
Nowadays commercial mowers share a lot of common components, so as long as you stick to quality built mowers, you'll be fine.
One last important point. When you negotiate, do it politely, don't insult the seller by "dogging out" his mower, or offering a ridiculous price, because you'll put the seller on the defensive and he will not want to do business with you!
Good luck and enjoy the "hunt"!