Go to a software/computer show if one comes to your area. I went to a computer show in Atlanta about 3 years ago, and some vendors and personal tables were set up and selling used copies of their older software which they had since updated. That's where I got my copy of Photoshop 7.0 (I already had it, but bought it for the books and manuals, and to have it on hard copy).
If you're just not starting to delve into Photoshop, I wouldn't recommend the latest version of CS2, or even CS. I'd say starting with 7.0 or 8.0. I still use 7.0 and 8.0 till this day for design projects I take on for customers, and for my own website graphics. It's just easier to manuever in I think, although the latest versions have some awesome features I wish the older ones had.
Here's a link to amazon.com where you can find version 7.0 for under $200.00
http://www.amazon.com/exec/obidos/AS...715215-9127044