Originally Posted by harryf
Its burning oil, needs either top end or piston/ring/cylinder work. Not necessarily a reason to walk away, but for sure factor an engine rebuild / top end work into the price. Ask how much oil it uses and you might get an honest answer.
For a classic with only a few thousand miles a year use there may still be a goodly amount of life left in it.
Don't forget though that you may come unstuck with your yearly MOT (if you're in the UK) or equivalent, and the examiner may not allow a pass if there is visible smoke.
If you plan on doing the work yourself, tot up the typical items needed from the Highwood or Classicalfa websites, and double the price, since you're bound to find other things on the way. If you're going to hand it over to a garage, be very careful or your 'investment' may turn on you!