Buying a used Xbox 360

Hey there, I've always been a PlayStation guy but I'm looking to buy a used Xbox 360 so I can play the Halo franchise. I'm currently looking at the older 360s (this one in particular: Xbox 360 Premium 20GB) as I don't a overly big budget so I'm wondering which Xbox 360s to stay away from just so I don't get hit with the Red Ring of Death. Also, if you can, let me know about any other issues to take note of. Any help is very much appreciated.