Try to find out how he went about rebuilding it. Did the engine chip a piston/spin a bearing/or kick a rod? If so stay far away. If it was a LIM repair and maybe just the front timing cover was leaking then consider it. If he did anything to the bottom end again stay away. From the pics on craigslist it looks like it may have a new front timing gasket, water pump gasket and the aluminum coolant elbow which makes me think the LIM was done. TRY TO GET MORE INFO.