Idling (also known as seeding) means you just sit in a server in spectator mode.
And by loot you must mean hats and weapons. If we were paid cash for idling I would quit my job and do that forever.
Edit: Stinky is way too slow in answering questions.
There are 'idle' servers & basically you join up, select a team & then go AFK. Thats it. Just be your account being logged into a server & on blu/red youll get drops.