Not a professor, just a B.A and M.A.
I taught some introductory courses (linear algebra, real analysis and algebra) for undergraduates at Oxford for a year.
Did some private tuition for A-Level students (don't know the US equivalent, but 17&18yos ).
After that i did a teacher training course and taught in a high-school for a few months. It was awful, that's when i gave up teaching.
The private tuition was ok though. So it's something i could always go back to if i go broke.