New clutch parts are around $350, $1200 w/ install. If the flywheel is smoked, then add probably a grand to that number for a new one, and if he's allowing test drives in that condition it probably will be.
Look for OFHG, Valve Cover, and Oil Pan Gasket leaks. Probably needs a walnut blast and plugs. Watch for long cranks, it's a sign of bad HPFP. If you have the PPI pull the plugs, you'll be able to tell if there is a bad injector.
The bad clutch will scare off every other buyers, and if he can't spring for it he's probably tight on cash. Ripe for negotiation.
EDIT: can you share the car so we can look at the post? If it's owned by the BMW Tech you mention in your other post, there may be other issues. Clutch job shouldn't scare him off.
This one?
https://detroit.craigslist.org/mcb/c...633970254.html