The problem is that even if the student really wants flight training and is just trying to manage his time efficiently, the FAA historically takes a dim view of instruction flights which have an obvious dual purpose. They cannot easily determine whether it's an instruction flight with business travel incidental, or business travel with instruction incidental.

Safest thing is to have the student provide the airplane...that way you are not in danger of running an illegal charter op.

Also I would agree that if the student has no medical, has not taken any PPL classes or the written test, you are on thin ice.