Check lock stop there made of cheese so if it's been down the road they bend real easy, make sure engine is sweet as mains can become noisey on the 848, make sure it starts ok and no smoke on start up.
Same as above, listen for smoke on start up and knocking mains (although the engine is quite noisy generally), check for all the standard stuff you would on a bike like head bearings and steering stops, signs it's been used as a track bike etc. On any Ducati with cambelts, check for history of them being changed as it's 2 years, I bought mine and they changed the belts for me even though it hadn't done many miles in 2 years and it's a good job as one had a crack in it. personally I would check the bike is cold and then get the owner to start it if it's private sale, always gives you an idea how it's been looked after! I would also ask if he knows what torque the rear hub needs to be done up to, a good test as it is often over tightened and ruined by lazy owners and isn't cheap.
Also try and find out if the bike has been recalled for the fuel tank problem. I bought an 848 a couple of years back , with a full 2009 Xerox WSBK paint and graphix job. Because the tanks are plastic (1098 included) ethanol eventually starts seeping thru making the tank porous , lifting the paint and graphix. Gonna cost a few quid to rectify as the sticker kit , which wasn't easy to find , was around £250. Getting the tank sealed with Caswell sealer is around £350 and then a paint job on top of that , so not a lot of change from £1k. chz
