There are many, many different ways to accomplish this. However, for a limited budget, I would personally go the route of purchasing a few hard drives and a few Mac Mini's, along with an Apple router. (This is, of course, keeping it within the Apple Family)
I'd connect the hard drives to the router, connects the Mini's to the router as well--maybe depending on how may you have, get a cheap little switch/hub for additional ports--and do the work on the main computer. When your ready to render, collect the files to the external hard drive, and put those mini's to work.
This would probably be the most cost-effective structure. But like I said, there are many different ways to do this. Hope this helps.
[Adam Duguay]"One Idea I had was to purchase a MacPro and run an instance of the A.E Renderer on it."
If you have a lot of RAM (3-4 GB per core), this could work, but one machine isn't even a render garden, let alone a render farm. There will be a lot of overhead associated with performing a network render, so if your total render power isn't substantially more than any one workstation's, I don't know if you'll see a return on your investment.
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