To say how much it needs would be a guess at best for us. One thing most of us would agree on is that it will need:
Carbs cleaned (not necessarily rebuilt but you won't know until you get in there
New Battery
Generally many electrical gremlins that most can be fixed with a thorough going over of all connections and cleaning them
New tires - even if they look good at 10 years old I wouldn't trust them!
Tank cleaning (maybe even a liner depending on condition but unless there sre holes an acid wash usually is enough)
new plugs and over all tune up (set timing, valve adjust, cam chain adjustment, oil and filter)
Also just as a heads up timing advance tends to stick after sitting that long in addition rubber tends to dry out etc so you may need more than at first glance.
Having said that though, most of these items are virtually free (except tires and battery) assuming you can do the basic maintenance yourself. I have found that most often carbs can be saved without rebuilding but some people always rebuild them.
I say go for it. Especially if the price is right. Obviously there would be additional costs associated with cafe'ing it but to get a decent runner assuming it isn't totally bodged usually is fairly cheap and can even be fun! (assuming you find busted knuckles, drinking beer and lots of cursing fun!!)
Dennis