Digital BW, The Print

I have Photoshop 7 currently and want to upgrade to CS or CS2 but the
price new is outside my budget (given that I just purchased an Olympus
c-808 and Epson printer) so was wondering if anyone has ever purchased
software like this on Ebay?  What should I ask the seller to insure I
reduce my exposure to problems?

My main purpose is to use the advanced functions to handle RAW images.

Thanks in advance for your help!