PhotoPass is free for anybody.
The PhotoPass system is simply a modern electronic version of the old roving photographer who gave you a slip of paper after taking your pic; instead of the slip of paper, you now get a photopass card.
When a PP photographer takes your pic, he swipes your PP card (if you don't already have one, each photographer carries a supply of new blank cards). Swiping the card associates that particular photo with that particular card. But you can swipe multiple cards for a single photo (in case you do a group shot and everybody wants one), and multiple photos with a single swipe (because the photographers usually take a couple of shots at any given time). Having pics taken is free, the PP cards are free, you never pay anything until you want to buy the pics themselves.
You can go to the camera shops in the 4 parks at any time to buy prints of any of your pics (it takes about an hour or so for pics to make their way from the photographers' cameras into the system). When you buy prints, you can have a choice of fancy borders or graphics added to them at no extra charge. You can also buy a CD with all of your pics on it at high resolution for $99, allowing you to have them printed someplace at cheaper rates than Disney's print prices, but these hi-res pics have no fancy borders or graphics on them.
But if you don't want to, you don't have to buy your pics or the CD until you get home. When you get home, you log onto the PhotoPass web site and create an account for yourself (this is free). Once you have an account, you can add the serial numbers from as many PhotoPass cards to your account as you want, and browse the photos from all of them to decide which ones you want to print. You can also buy the CD over the web.
Each member of your party (or family) should have their own PhotoPass card. This gives two advantages: 1) When you get a family pic taken, the pic can be associated with all of your cards, reducing the possibility of the pic getting lost in the PP computer system (this happens sometimes), and 2) when you split up to do sepparate touring, you all have your own cards and can get pics taken wherever you go.
PhotoPass photographers tend to hang out in the big photo spots in the parks - at the 4 park entrances, at the Partners statue, on the walkway from Future World to World Showcase, and a few other miscelaneous places.
Ride photos will be added to the PP system soon; right now, only Test Track is part of the system.