I make NFL lamps. I have been to a game at Met Life Stadium. And saw many people selling team stuff. When I go I might bring 20. Will I be hassled by mgmt for selling them. I'm not even staying for the game ?

Do it in the parking lot. They will kick you out if you do it inside

Parking lot should be fine. There are rules on bag size in the stadium

If the they see you doing do inside the stadium you will be asked to leave ...the parking lot maybe different

I don't think so. They were selling hats, cigars and other products. You should be fine.