Bartender

newreel -
I would suggest that you start working hard at learning Linux, because the folks you're helping are going to have LOTS of questions. Not so much because Linux is impossibly geeky. Maybe just a couple of years ago. Not so much now.
But Linux is not Windows. That one sentence covers a lot of territory, and those who haven't explored that territory will be frustrated.

What you're doing sounds like a very good thing. Might as well prepare these folks for the OS of the future, instead of them wasting time on Microsoft.

You should get up to speed on OpenOffice, the amazing alternative to Microsoft's cash cow Office Suite. Did you know IBM is now partnering with the OpenOffice folks to provide an "IBM version" of the OpenOffice suite?

If you're not already using Firefox as your browser, install the Windows version to your PC and start using it. The Linux Firefox is a little bit different but similar enuf to figure out once you're up to speed on the Windows version.

Install Thunderbird to your PC and start using it. If for one reason or another you don't want to get your existing e-mail via Thunderbird, start an e-mail account at GMail, get some friends to start sending e-mail to that address, and follow the very good directions available at the GMail website to configure TB for GMail. There are lots of neat little settings in TB that take some time to figure out, and you'll want to have some familiarity with that so you can set up other people's PC's.

Those 3 programs will cover word processing, internet access, and e-mail. I figure those are your clients' basic needs.

I agree with what's been said above - there are stripped-down versions of Linux for older PC's but the "easy to use" part rapidly goes away. I've plinked around with older PC's and would say that a Pentium III 700 MHz or above (or AMD equivalent) is about as slow a processor as you'd want to go. Some things happen so slowly on my PIII 450 MHz test PC that you'd think it was broken. It's not; the CPU is working at 100% and one just has to wait.
You can't have too much RAM. Cheap old PC's often have 128 or 256 installed, and the motherboards don't take much more. This is a problem. If you can scrounge up extra RAM do it. AFAIC 512 is a minimum for a fully-featured Linux OS.
We're talking low-income, right? Which means dial-up? That's gonna be a problem right there. Dial-up is still a pain in the Linux world. I don't want to go into it right now, so write back and tell us what's going on as far as internet connection, OK?

EDIT: Make sure you have a stack of good-quality 700 MB CD's for burning your .iso's. The older 640MB CD's won't work.