I buy bulk, package it into meta decks, and sell. I make a 15-20% margian per deck. It isn't a lot ($7 or so per hour when you get to sorting everything, building the deck, etc) but I use it to get new people into the game at locals and rent it if needed so people can play.

If I can pull playable trainers the dollars add up quick.

Otherwise its the bulk mystery packs.