Know-How Exchange : Advertising/PR

Basically, my company manages a bunch of doctors offices/physical therapy locations through NYC and Long Island. We are looking into installing TVs in the offices mostly just to have advertisements running—we have about 20 offices treating 12,000 patients each week. I've tried searching google for information about this type of advertising, but can't find anything that begins to paint a picture of the financial end of this endeavor. So really any information about someone I could contact or the kind of ad revenue we could expect from this would be great. Thanks so much in advanced