What kind of money are you looking to spend?
How much water and food do you intend to carry?
If your just wanting a knock around quad for doing back and forth jobs - get an old knock around quad - the things you dont really need to look at and can knock people down on price is things like split drive boots, electrics not quite right, worn tyres on the braking wheels (turn them over for another 5 years wear lol), bodywork damage - as long as it starts well and every gear works thats about all thats important.
My ugliest most worn out quad is my favourite - bashed to hell and back - been rolled by about everyone except me. (I just have to fix the bastard after).
Your more often than not better off buying an old cheap honda or susuki than any spending a little more cash on an 'old' newer imported atv as parts for hondas are easy to get and cheap as chips.
All old 4 stroke hondas will be seeping oil from the rocker cover gasket and smoking from the engine exhaust - just have a quick look over the engine and make sure there are no rounded bolts, nuts or screws for the future.
I wouldnt be able to do without a quad - you'll love it when you have one - you wont know what you did without it (well you will in winter when it wont start and the battery is flat, but you get what I mean)
Baz