Thanks Derrel, I will have a look at those as well.
Is there anything else other than some 120 film to make these work? (dumb question, but have zero experience with this)
All one really "needs" is film; the 124G has an on-board light meter powered by a
small mercury battery, which I believe is no longer available. I have a Yashica 635, circa 1958...it has NO light meter, and thus requires nothing but film, no batteries, nothing extra, in order to shoot film. I listed the Yashica Mat 124G as being a good choice simply because it was a proven and widely-manufactured Medium Format camera with simple operation and falls within your budget zone, and is NOT a "collectible": like so many Rolleicord or Rolleiflex TLR's are. Here's a post with a wee bit of info about the 124G and its battery/meter situation. The shutter is NOT powered by batteries, but is 100% mechanically-timed.
http://photo.net/medium-format-photography-forum/00T89