I think a good choice for under $500 would be the Calumet CC-400 monorail. They're common, and for that price you should be able to find one complete with lens & shutter.The CC-400, the standard model, has a 20-in. bellows; there is a long-bellows model, the CC-401, and a short-bellows model, the CC-402. These cameras were made between circa the mid-'60s and mid-'80s especially for beginners. They have all the movements (axis tilts) except for back rise & fall.
The CC-400 was my first large-format camera. It allowed me to learn all about movements. They're sturdy, no-frills cameras. There's a previous thread on APUG about the 400 series:
http://www.apug.org/forums/forum44/5...-beginner.html
Lots of info about these cameras on the internet. They're probably the most common 4x5 monorails to be found secondhand.