I've owned a few 5234's since 2004 when they first came out and never had a problem. There were some issues with some of the tractors, others had no problems. I plowed a lot of snow this past winter with my 2007 and it performed flawlessly. Check the tractor out real well, take your time on the test drive, check all fluids, check the differential lock, 4wd, PTO's, etc. Check the tranny for a new seal.
I JUST listed my 2004 5234 with 41 hours on it, it runs like a top, been sitting in my garage for a year.
A big concern (to me) is if it has a loader.....I consider the 5000 series a light duty sub-compact.....(tractor only weighs 1300 lbs) so if you plan on doing a lot of heavy loader work, be careful. Having said that, my first 5234 had a loader, and I used it quite a bit with no problems. Now I use 2 bigger Cubs for loader work and use the 5234 for mowing/blowing/blading. I'd try it out before I ruled it out! Good luck!