There are free 30 day trials that you can download.
Version 7 is not free, as far as I can tell. Not sure where you got that info. Unless you pirate it I guess.
Photoshop Elements is a cheaper alternative designed for home use. It is not as powerful as Photoshop, but it has a lot of the same features. Photoshop is a professional-level application, not really designed for home users, which is why it’s so expensive.
On the Mac there is Pixelmator which I’ve come to really enjoy. It is much less bulky and much faster than Photoshop and has most of the same features. There are still a few glaring omissions like adjustment layers and the like though.
Also Acorn has a pretty good following on the Mac.
On the PC there are things like Paint Shop Pro and others.
The Gimp is horrible in my experience. The interface is atrocious and hard to use and it just doesn’t “feel right”.
Obviously if he is taking a class in Photoshop then none of these alternatives are going to work, as the class will be all about Photoshop, not program x.