My opinion (I am new to this) is to get the refurb model from Apple to get the one year warranty on the product. I would say go for the Apple Care, too (I think you can do that) but I understand you are on a budget.
I got the mb471ll/a from cowboom a few months back for $909 for reference. I have had pretty good experience with ebay, just make sure you are buying from someone with a lot of feedback that has sold computers before.