I will describe my experience with Countach maintainance. I have driven the car (hard) for long periods in between major maintainence expenditures, and once a Countach has been fully gone through they are very strong and reliable cars.
Having said that, let's define the budget.
Most garden variety problems are $150 to $1000 issues. The problem is that sometimes it will take a $300 flatbed movement and a bunch of time to get to the shop for the aforementioned attentions.
Unless the car you are buying has been fully gone through and refreshed, it will eventually (sooner than later) need it. Remember these are 20 year old cars, and they have either worn out stuff (even with low miles) or have so few miles that seals have shrunk, hoses have become stiff and brittle, etc.
A major service (major components are valve clearances, degreeing the cams, cam chain tension adjustments, and induction / fuel set up) is around $3500 to $5000 for the basic service, and expect to find $500 to $2000 of stuff requiring attention. Once a major has been done, that stuff is probably good for 15,000 miles on the outside.
The clutch is an $8000 item, rebuilding the tranny (20,000 to 30,000 miles is what you get from a set of synchros) is a $2500 item (once the engine is already out). If you end up doing this, it will probably last the life of the car as you know it.
The original ignition box will go out and $1500 or less gets you a noce MSD box to replace it (which is way better than the factory box).
I bought my car from a guy that did a lot of his own work, and had it set up pretty decent. I drove it for several years (including some pretty hardcore high speed rallies) before putting he car in for a complete go-through.
About $35,000 went all the way through the car including the above mentioned items and about everything it took to refresh and update every system in the car. I expect to drive the car about 5 years before needing to do much more than oil changes..... eventually I'll need to do a head job and oneday rings.
I figure I'll see a $400 to $2000 problem every year (electrical glitch, replace shocks, whatever).
Overall, you'll be okay if you take the assumption that a Countach is a $100,000 car whether you buy it for $50k and put $50 more into it, or buy one that's been just gone through for $100, the number will be at $100k within a few years of buying it if you drive it much or drive it hard (which is the only way to drive a Countach!). Then once the car's up to snuff you won't see much more than oil changes for years at a time.
Good Luck-
Steve L
'85 COuntach QV