Thank you all for your input. The aircraft (any of them) will be rented through the flight school by the student and I get paid by the flight school for flight instruction. I've been told that if I sit around at a FBO for 3 hours waiting for him, I get paid for "pilot services" at the same rate as flight instruction.

I agree with you 'jonnyjetprop', one client is not worth my pilot certificate.
I've told him about the medical, he should have it by his next flight and will tell him about the written exam too. I plan to have him solo on the single engine. He doesn't just want to fly to/from meetings, he wants to get his private pilot certificate but also wants to take advantage of having an airplane to save time. I have a syllabus that I carry with me on all flights to document what was done on the flight lesson and I also enter the date on which the flight was completed.

On another note, he threw up on his first flight in a C-172 a few days ago and says that he has motion sickness when he does not have any visual references, so I'll see how he flies under the hood on his next flight.