Sorry, I have to say that although PSCS2 is expensive it's well worth the money, moreso if you are planning to do much professional level editing. Yes, Elements has it's place, but layer masks alone will make it worthwhile once you get the hang of those. Plus Smart Objects is fantastic if you do layout work.
Part of the answer to your question depends on what you need to do. If you start with Elements and end up buying PSCS2 in a few months you won't be saving anything. Here's a link to a comparison. Like it says, there are workarounds for a lot of the differences if you go that way. You can also look at educational discounts, etc. to help offest the cost.
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