Used Digital SLR for Teen Beginner?

I want to get a used (read inexpensive) DSLR for my 14 year old girl. She has shown aptitude and responsibility with a borrowed camera. It would be nice to get into a product line that lends to upgrading - accumulate a few lenses and other accessories and eventually step-up to a more sophisticated body. But that's not required. It would be equally desirable to just get a lens and body that are easy to resell once the commitment to photography has evolved, and then move into whatever makes sense at the time. A quick-take has led me to the Canon 20D. A newer camera, the Olympus E-520 came on my radar today as I perused used cameras at stores in downtown Osaka. With the weak US $, both the 20D and E-520 seem to be in the mid-to-upper $200 range before tax. Maybe a bit less a Nikon D50. Although I love the selection in Japan, I think I can do as well back in the US, and I'm leaving today. Plus I'm not informed well enough to make a purchase yet. All three of these bodies are available on eBay for less than $300 right now. So with that price range in mind, would you care to weigh-in on which would be the best choice for my situation. Other cameras?

The 20D

I have the 20D, and I love it. It is a great camera. The body is mostly magnesiusm, so it is stupid durable. The low light performance isn't something to rave about, but that is understandable for a 7 year old camera. It takes both EF and EF-S lenses, so you can find a rather large selection of those on website like ebay and B&H.

Oh on a side note about the 20D, when you get it, if the shutter makes a really loud noise, don't worry. The 20D has a rather loud, distinctive mirror slapping noise. Not sure why. The 10D and the 30D are relatively quiet, but the 20D sounds like a full on slap.

Don't buy a Used SLR's. Just buy a new D3000 for an entry camera. Photography is an expensive hobby