We, too, went the ZTR route about 20 years ago -- one at a time, we went through three used commercial units we bought off a brother in law with a landscaping business. He beat the living daylights out of them but they were pretty good and a bout the same price as you'd pay for a new, good rider. They were Toro Z Masters with Kohler engines. All we ever needed to replace were the steering dampers. In 2011, for the christmas tree farm, we decided up get a new ZTR, and for a number of reasons, ended up with a diesel-powered commercial ZTR (JD 998) which turned out to be absolutely the right choice, but that's a whole different situation ... But the Toro it replaced is still around. By the vagaries of fate, it is back on our old farm -- the new owner bought it from the people we had sold it to. Has a new Kohler engine, but otherwise is working fine. One rugged machine ...
My point -- There might be some good deals available on used commercial units. My BIL had to turn over his equipment before it was worn out for accounting/tax purposes. Other landscapers might be in the same position. Those units may be hard to find if lots of other guys know all of that ... But on a used commercial unit like a Kohler-powered Toro Z Master, don't let looks deceive you -- it may look like a bombing range target, but it might still be in good condition. If the engine is good, the rest of the mower probably is, too. With our beat up used commercials, I never had *any* issues with the hydraulic systems (wheel motors, pumps, lines, etc). I had to replace a few mower spindles, but that was operator error
There are some good commercial units out there (Toro, Dixie Chopper, Grass Hopper, Scag, etc) See what the pros use around you and check if any of them are planning to offload inventory at the end of the season or whatever. Right now is probably not the best time to be shopping for any kind of mower
And if you think a John Deere diesel ZTR is expensive (and it is, actually), try pricing a Steiner some time ....
On any gas powered ZTR, look for a Kohler engine. I learned on the farm that Kohlers work, the others don't (with the notable exception of Robin/Subaru and Honda, but I do not know if they power ZTRs yet ...). You will pay nearly double for a quality ZTR that you will pay for a quality tractor-type mower, but if time and convenience matter, you will find it worth the investment.
There is also a BIG difference between "Lawn tractors" and "Garden Tractors" in that Garden tractors are built more ruggedly.
I've also heard that mowers sold by the big chain stores are low-end lines of lesser quality than you will find at ag stores or equipment dealers.
Good luck, Ron. I've never met or talked to *anyone* who regretted stepping up to a ZTR -- even a Harry Homeowner one.