Bob, I don't think discouraging me from what I want to do when you don't even know my plan is very a wise move.
That said, you didn't even answer my question. I'm just looking for a ballpark figure on the minimum units a conventional printer requires.
The difficulty is that it's a poor question. You're still at the point of research where you don't know what you don't know.
"Conventional printer" is a meaningless phrase. They're all conventional. Are you talking digital? Letterpress? Linotronic? Offset?
They all require different minimums. Moreover lintronic or offset printing will also require a setup fee, which means it's cost effective to order the largest possible print run you can, which will also result in lower costs per unit.
Other things to know in advance, besides pagination, is what kind of cover you'll want, in terms of color set up and print quality, as well as paper.
Binding will also make a difference.
The smallest print run I've done on offset was, I
think, 200, but it was prohibitively expensive and only worth it because it was a limited high-end scholarly book with tipped in illustrations.
Finally, read
The Newbie Guide to Absolute Write. We're serious about the respect your fellow writer.
You might be better off getting a rough idea of how many pages your typeset book will have, and start looking at printers' web sites. Call a few up and get quotes. Be honest and tell they you don't even know where to start. Be aware that there are great printers and really bad ones and some that are crooks. Check your local area first; you're more likely to find someone will to work with a customer who won't know how to prep the file for printing, etc.