Originally Posted by
Bucknut
There are advantages and disadvantages to doing this. You have a vested interest and will bring more experience than a freshly minted CFI.
He might have more experience than a freshly minted CFI, but a freshly minted CFI is probably a lot more knowledgeable about the things actually being taught for a private pilot certificate. Not that he can’t regain that knowledge, but it will require some studying and some practice flying light aircraft if he hasn’t done so in a while.