Your question is similar to asking this question in a gardening forum: “I want to buy a car for $5000 to use for my landscaping business. What should I get?” The best answer would be: “get at least a station wagon to carry your plants. Maybe a van or pickup. Beyond that, it really doesn’t matter if you choose a Ford, Chevy or Dodge. If you have other car-specific concerns regarding dealer network, parts availability, fuel economy, you should post in a car forum. Sorry, this is a gardening forum”.
The only AE-relevant advice I can give you relates to keying. For $1000, the best you can do is buy a DV camera, then buy DVmatte pro from DVgarage to key the things you shoot on greenscreen. For the money, DV is your only real format option. Camera make, lenses, features really have nothing to do with AE, and more with videography, which is covered in other forums. Fancy image-effect camera features are irrelevant in my opinion, because you want to shoot a clean plate for compositing in AE.
Not meaning to be anal, but this is a high-traffic forum, and new posts push the old posts off the screen. If we stray off-topic too much, the on-topic AE posts will be crowded off the screen.
Steve 🙂