You had better think parts, then parts again before you buy. For that kind of money you can get a grey Yanmar in the 18hp range, 4wd, with a new Koyker loader, overrunning coupler, and an OSHA approved ROPS. We have a 159 page catalog of aftermarket Yanmar parts. There is no such thing to our knowledge for Kubota (or any of the other Japanese brands) and Kubota USA dealers are under orders not to provide service or parts for grey models. Anything you buy will eventually need parts.
Regardless of what you buy, insist on references from where ever you're considering buying...actual references you can contact, some a year old or more (most folks are happy at first). Does the seller provide a copy of your tractor's parts book (we do, as well as a 6 month warranty), and can they access most parts you'll need? Be very, very informed before dropping a chunk of change like that or you may be very disappointed down the road. Good luck.