The current computer based MCAT started in 2007, so anything from 2007 forward is fine.
The basic structure of bio sci / phys sci / verbal has been around since 1991 so you could theoretically get practice materials that are 22 years old and still get some useful practice from them. I'd recommend against it, though, since there have been enough tweaks and stylistic changes that those really old materials will give you a slightly "off" sense of the test.
If you're concerned about cost, there's a LOT of good free stuff out there: wikipremed, mcat-review.org, mcatforme, wikipedia, khan academy, aamc outlines and Test 3, couple of MCAT question-of-the-day sites, free practice tests from KTP/TPR, etc.