The best/first reference for a majority of these questions that we're going to bring up is FAR 61.23 Medical Certificates: Requirement and Duration .
An example of a question we get is "I'm going for my Commercial ticket, do I need to have a 1st or 2nd class medical for the practical?" The answer is no, you do not have to have a first or second class medical for a Commercial practical test, all you need is a third class or BasicMed. But you do need to have a 1st or 2nd class to exercise commercial privileges.
As pilots we memorize the duration of medicals, and what class we need for that particular certificate we're going for, but not always what happens to those durations when we hit 40 years of age or what class medical is needed for after we hang up commercial flying and we're just giving flight instruction part time.
Since we get this type of question a lot, I wanted to open this up to anyone that has questions about medical durations or privileges, and may not want to take the time to create a post to ask a question themselves.
Scratch At AOPA:Island Boy At AOPA:
I'm very glad you brought this up. We get many calls from pilots thinking they require a 2nd Class medical to flight instruct when instruction can be done with a 3rd Class medical and with a BasicMed qualification.
You can instruct as well without a medical as long as you don't need to be PIC or safety pilot.
Here are the legal bases for all that CFI/medical stuff.
https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/data/interps/1995/Fretwell - (1995) Legal Interpretation.pdf
https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/Data/interps/2018/Williams - (2018) Legal Interpretation.pdf
and to support Scratch:
also in GRAU....https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/Data/interps/2010/Grau - (2010) Legal Interpretation.pdf
Murphy https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/Data/interps/2008/Murphy - (2008) Legal Interpretation.pdf
Rubin https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/Data/interps/1991/Rubin - (1991) Legal Interpretation.pdf
Remember you have to accomplish a Third class between July 1 2004 and the current, to be eligible for a Basic med. Exercise of teh Commercial certificate for any but for instruction CANNOT be accomplished with Basic Med.
You'll have no difficulty with the small GA ships- but once you get to twins, the insurance will be problemmatic once you get to twins. ANd the owner will be quite reluctant to turn over "legal control of operation" to a pilot with a lot lot lower Multi-time than he.
So you can do instruction, and be paid for your work- but there are caveats.
See the FAA Basic Med FAQ:
Q24: Can I exercise my CFI, as PIC, under BasicMed?
A: Yes, as long as you are flying a covered aircraft
The legal logic is that Gandy and all those other interpretations still apply, but the fundamental issue is that when you're giving instruction and getting paid, you're getting paid only for the training, so you are only exercising Private Pilot privileges for any pilot duties you perform at the same time. That's why 61.23(a)(3)(ii) allows instructors to work with only Third Class or even just Basic Med when acting as PIC under 61.113(i).
In, Gandy it was held that "It is also made clear that when a CFI is acting as PIC or as a required flight crew member at the sate time they are giving flight instruction, they are also execising the privileges of their pilot certificate. Whenever you exercise the privileges of your pilot certificate you are required to be the holder of an APPROPRIATE current medical certificate (FAR 61.3)....you must necessarily hold a medical certificate.....
Fretwell: "61.10 states in pertinent part that a flight instructor certificate is effective only while hold has a current pilot certificate and a medical certificate appropriate to the pilot privileges being exercised.
These two are still up on the O&I site. I would expect them to to have been removed.
Murphy: "accordingly, the current regulations require the flight instructor to possess a third -class medical certificate when engaging in flight instruction and acting a PIC or as a required flight crew member." They said they were going to take it down, but they did not! .(..ed)