Yeah, there is a great chance this could easily fail because there aren't that many people who want to learn Linux and if they do, I doubt they're willing to learn it exclusively on command line.
Maybe there's a way you could try the idea out with a lesser number of computers just to see how it would go.
If you do this, you'd need to make it very clear in your eBay ad there's no support included, unless of course you intend to include support. If support is included, you can probably expect to hear repeatedly from at least 48 of the 50 computer buyers because they will run into issues. Failure to provide the expected help could cause your feedback score to bottom out.
I don't know... perhaps I'm wrong, but then again maybe I'm right. This is why a lesser number of machines might be a good idea for starting out.
Just my thoughts on it. Good luck, no matter how you go with it! Cool Smile
Like the most recent post says, Slackware will most likely be faster on low-end computers, there is nice book on Slackware too which will be able to answer a lot of questions.
Just to add to my above post... if it were me, I'd probably install Ubuntu, Mandriva, or Fedora on them rather than Slackware. Not because it I think they are better than Slack, but because the buyer would more easily obtain any needed help/support. I would actually prefer Slack if it were me buying one.