Hmm...I've seen several broken hubs on the older RZR 800's but not the ATV's. PO must have been doing some jumping and rough terrain.
Having seen that, I'd probably use a bright light to inspect frame joints and a arm brackets for cracks while I was down into it. If you catch them BEFORE they break its a pretty simple fix.
I've got an 06 800 that I've put 17,000+ really rough miles on last few years. I bought new this year but kept the 800 as a backup or for friends and family. Don't hesitate to ask questions about anything you find. I've turned every bolt and screw on mine over the years.
I rode it several years claiming, "I don't need no stinking PS".
After I installed the Super ATV EZ Steer kit I couldn't believe I'd tortured myself needlessly all that time because I was too tight to shell out the $700.
Best money I ever spent on that machine other than tires and wheels!