From a brand new zt convert; mowing five acres with any tractor is insanity, unless you really really like to sit on a mower growing basil cell carcinomas' (sp?) even with a 12 volt cooler with a six in it-thanks but no thanks.
When my brand new Quest will start I can mow our 3/4 acre yard and my neighbors-about the same size-in much less time than it took me to mow just ours with the Simplicity lawn tractor and it had a fairly tight turning radius, 14" or so.
As for used equipment; what I found is that the prices are nuts, especially JD, in a year of serious Ebay/Craigslist hunting not a single unit turned up that was priced low enough to make me buy-for about another 1000 bucks whatever model advertised could have been bought new, broken in by me and maintained by me. The John Deere models, without exception, could have been bought new for about $500 more and this included some units that were 5-10 years old, fancinating really.
Plus, there are some really-really-really wierd people out there, I am a 'well nourished' person, my docs description not mine, just over six feet and I have a very 'diverse' background and I went to a few addresses where the people made me a bit uncomfortable, and I still carry.
My advice; go only during the day with a friend AND be certain ownership can be proved BEFORE you put a desposit on any equipment-one situation got real ugly on me fast-I am afraid that you will find that there are many very desperate folks doing what they have to do to either survive or support a habit-or screw the spouse out of assets.....
On ebay especially the most frequent scam I encountered was to place the 'winning' bid only to have the sale withdrawn-insurance fraud I am certain and Ebay does not care.