I've been using Pocket PC's myself for years now, so I'll just answer from that point of view.
First of all, he can do a lot better than a written list a la Notepad. There are specific list-making applications that allow one to do a lot of stuff that might be of help to your friend. One of the big list apps would probably be
ListPro (which I notice now is available for Palm and would probably work fine on a z22). There is an option to buy both a PC based app and a Palm / Pocket PC based one, and that would make creating the list easy (on the PC with a full keyboard etc) and then referring to it and/or making minor changes to it on the go.
Listpro is just something I happened to know was out there and have tried so it may not be the best, but it's pretty darn good and would run on a z22 from what I can see.
Another option, if paying for a PDA seems pricy, might be to look at what Phone+PDA combos are out there. A Pocket PC based phone would give him a fantastic phone and contact list device as well as a platform for price lists and whatnot.
But yes, a Z22 and something like Listpro should work nicely, and not break the bank.
I'm not very aware of what apps are available for Palm, free or otherwise, but you could always browse around on
http://www.palmgear.com and see.