Originally Posted by rickair7777

Correct, getting paid has nothing to do with it.

Legally you do not need any medical at all to flight instruct, UNLESS you are the required PIC on the flight. The CFI does not need to be the PIC if the student has a PPL or better in the aircraft and is rated and current for the flight conditions.

You cannot do these things:
Student Pilot training.
Instrument rating training in IMC (VFR hood training is OK).
ME rating training (or tailwheel, etc).

You could legally do these things (insurance may be another issue though:
BFR
IPC or Instrument rating (VFR hood only)
COMM, ATP, and CFI training
Aircraft familiarity checkouts


This rule exists to allow older, medically deficient, but very experienced pilots to instruct in conditions where the student can assure flight safety.