[Observing]

True story.
A lot of football coaches are also athletic directors and conditioning or PE "teachers".
After you add all of it up, its a pretty big salary.

Theres also boosters and parents that like to write checks in some places.

There's nothing wrong, legally or ethically for boosters to
augment a coach's pay if that's what they want to do.
Of course if they hide it and the income doesn't get reported
that's another situation.