Folders in good shape can get costly especially if they have range finders built in. I use a TLR Mamayia c220 and a prism view finder and it's served me well for many years! It also gives you lens interchangeability if you need it. Good luck with your search.
I'm surprised that so many people are recommending TLRs, when the man has mentioned that he would like a Bronica RF. There are lots of other medium format rangefinders that he could try, including the Koni-Omega and Rapid-Omega cameras in 6x7, which are quite reasonable and have excellent lenses. A 6x9 folder would have an aspect ratio familiar to a miniature format shooter and would also make a good starter camera. The last thing that I would recommend is a TLR, with a square format which will seem foreign and with a viewfinder which will frustrate him with the "backward" movements to frame the picture.
If you like a 40mm on 35mm and want a RF then one of the Fujis is the obvious choice. The big 6x9 with the normal lens or the smaller 645. Either is cheaper then the wide lens models. Should be a fair bit less then the Bronica RF.
I would put a word in to stay away from the "Seagull" TLR being sold by the lomo people. I borrowed one to try when I was looking for my first "real" 120 camera (as opposed to my beloved original diana and other oddities). I found the Seagull, at least the one I had my hands on to be a real mess – especially at the prices they're charging for them. The film counter didn't work properly and the lens was nowhere near as sharp as I wanted for medium format. I ended up getting a great deal on a Mamiya 220 from a fellow on photo.net and it takes beautiful pictures. It's got a bit of a learning curve with the bellows action and paralax adjustments (and it's extremely heavy) but it's a lovely, sturdy camera – and you can get different lenses for it even though it's a TLR. I would recommend taking a look at this one, or other Mamiyas. I think you can probably get something of great quality for not a lot of moula. Have fun!
If the OP really wants a decent modern rangefinder camera then the Fuji GA645 series is about all he can get that is significantly cheaper than the Bronica. Folders are likely to be hard work, especially the zone focusing (and RF ones are way overpriced). A MF SLR is definitely a non-starter if you want to be discreet – one of those babies could wake the dead.
TLRs are discreet, often cheap, but tricky to learn how to use. Having said that my first MF camera, if you discount the Brownie 127 I had as a kid, was a Yashicamat TLR. It gave decent results before it fell to bits...
For street shooting TLR's are good ,(the less professional looking the better), with the waist level finder, you are looking down into it, not at them, (you're subject) you can also point one way and the camera the other, and above all they are quiet