Originally Posted by Da40Pilot

Gotta disagree with you on that one, except the part where you need chief pilot approval. The time that you log as a flight instructor is the one and only time that does NOT count towards 117 rules. Meaning, you can pretty much CFI as much as you want on the side. The 117 rules apply if you're going to be doing part time 135 or 91k stuff.

He'll need to get an LOA from the chief pilot's office for sure, but apart from that, he can flight instruct as much as he wants on the side.