I wouldn't pay to have your stuff placed. If a company wants to take a cut of the payment after it gets placed, that's normal, but don't pay in advance.
I've dont alot of TV work, I've never paid for placements ever. I work with the advertising company directly. Your best bet would be to try and establish a relationship with the people who collect the music for the ad agency, at least for TV. I've been wanting to get into games, but I don't have a plug!