As the owner of an E-body I can tell you I agree with what's been said so far, they're expensive!
If you're looking for a drivable e-body, plan on parting with at least $10k. Thats about what I paid for mine, and since then I've been watching Ebay and Craigslist and all the local stuff (almost a year now) and I can say if you want something you can drive it will cost that much. Even rollers with most of the parts will set you back $5k depending on the condition, and that's just the regular run of the mill stuff, no R/T's or T/A's or anything crazy.
I bought my '71 Dart GT, an original CA car, no rust, #'s matching, with buildsheet, and in need of a carb rebuild and some interior parts to get it back on the road, for a little over a tenth of what I paid for my '72 Challenger, a non-numbers matching, no buildsheet, needing floor patches and 2 small frame patches, driveable 318/904 car. My Dart is in far better condition that my Challenger, although the Chally looks better from 10 ft because of the lame Maaco paint job (it'll fall off soon enough).
Other than the price though, the e-bodies have the same number of quirks as the a's, just different. Bigger and heavier, thats for sure. Harder to find than the A-bodies too, same for parts. Avoid rust like the plague, the body parts cost a small fortune!
If you want to find an e-body, just plan on looking for awhile. I bought mine too fast, got excited and it was close so I picked it up and have been caught by a few things (the frame patches it needs!). I've seen some pretty clean cars out there, but like I said, plan on parting with at least $10k if you want to drive it. The '72-'74 models are definitely cheaper too, so if you're on a budget look there, the '70 and '71 cars are usually more expensive because of the BB's and the special models. A lot of parts on the '71's are '71 only, so parts can be an issue on those (REALLY expensive). Also the coolest year IMHO, go figure.
I love my e-body, my bank account hates it! Good luck :-D