This is a carbed motor, with a two-barrel, no less. It may well not have a perfect idle. I mean, it shouldn't be too rough, but a misfire at idle every now and then is nothing to worry about. My car certainly didn't idle perfectly when it had the 45 DCOE. It's all in the tuning.
White smoke at cold startup could just be steam from condensation inside the exhaust and such. You've only got bad coolant seals if you're actually losing coolant. If the exhaust smells "sweet", that indicates bad coolant seals.
From the sounds of things the owner isn't clueless. It's a decent deal if the damage is minor and it passes a ghetto compression test. But you'll have to be willing to get your hands dirty.
