My recommendation is to find a good clean EOS 620. Takes all EOS EF lenses, has autofocus, sturdy metal body, large contrasty viewfinder and simple controls, with easily replaceable battery and lots and lots of old examples around - try Craigs List or Ebay, if not local camera shops used departments, camera shows and thrift shops. A very nice clean one will fetch between $30.00 to $120.00, depending on who is selling it and where it's selling. This was a high mid-end enthusiast camera when it came out. See" http://kenrockwell.com/canon/film-bodies/eos620.htm
to learn more specific details. Generally, it's going to sell for much less than any of the pro EOS cameras of its era, or the ones from a bit later, and be almost as good performing and rugged in use as the pro models, except in autofocus performance, which you should probably not really be using very often anyway, if you really want to learn to master photography, rather than learn to pilot an auto-function camera. They don't make mid-level cameras with construction like the 620 anymore. I bought my son this camera with a new cheap "normal" zoom to go with it for his introductory photo class about 5 years ago and the thing is still going strong. The camera body was $75.00 from a good local camera store and the less than stellar 3rd party zoom lens was another $75.00 or so. Your experience will vary. And don't be afraid of getting a used beat-up looking and now discontinued model Canon EOS lens (I coundn't find one when when my son needed it); if it works properly, the bad cosmetics are only acting in your favor, lowering the price for you because many others would be too worried to take a chance on the bad cosmetics.
If you want even better construction, can live without autofocus and don't mind digging around for some older FD lenses later on, get an even older top-of-the-line professional Canon F-1 - or the second series "new" F-1 - with a lens or three in a kit for sale on Ebay, or from the same sources mentioned above. That was a great camera and using it as an all manual camera (both focus and exposure) is very very easy and a great experience for anyone trying to learn the actual craft of photography for the first time.
Whatever you do, don't buy one of the later, flimsy plastic EOS Rebels, which were comparatively poorly constructed and not as nice in many other ways.