You should, at all times, be able to swallow a $5000 repair bill without that bill ruining your love affair with the car. The probability that you will need to outlay to such an expense is rather low, but you need to be prepaired nonetheless.
5K would be great. I just bought a TR with 22K miles . After a major, new clutch, new fuse panel, new a/c drier, new hyper flow cats(want not need) , new x-ost maranello muffler(another want not need. The parts and labor were close to $18K. This is my 3rd Ferrari so I knew what to expect when I bought it but still multi thousand dollar repair bills are a reality and as I told my wife, I never bought one of these cars because they were cheap reliable transportation.