If any of your triggers were to go full auto, even by accident, you will be going to big boy jail. I am not sure, maybe one of the practicing gunsmiths on the forum can tell us if you need a federal license to practice in this area, seeing as you wish to do it for profit. Good luck anyway
A few days ago I posted a thread about polishing an AR-15 trigger group. The thread was closed before I could post the pictures I took a few hours ago. Here are some images of a trigger I polished 3 years ago with at least 3500 rounds though it. The sear could have been polished a little better, and it does show a little wear. The hammer engagement looks as if I polished it yesterday. The lower still breaks nice and clean.