At the flight school I'm at, we bill for ground lessons as well. I do 1 hour of gound with my students for every 2 hours of flight. You'll find that crummy, Part 141, Cessna CMM TCO at many flight schools. Whereas this helps you cover your @$$ when it comes to getting your students ready for their check-rides, it only covers the basics. Don't expect your students to do well at an airline interview if you leave them only with the information gleemed from the overly simple Cessna video lessons. Having gone to an airline affiliated flight school to get all my ratings up to CFIi, I am shocked by how little most of my BFR applicants know. My point here is there are "grounds" and "sims" you can do that don't take quite as much out of you and should comprise 1/3 of your income if you dont land a salary CFI job.
BTW. I find one of the biggest flaws with the Cessna CMM courses is that you NEVER see the guys flying the airplanes use check lists. EVER. This encourages very poor flight discipline and lack of procedure.