Singer 111W151
 

Look, you can get one of these for $100 and he has four of them .... although they are a bit dusty!

http://greensboro.craigslist.org/bfs/4427123072.html

Around here industrial machines go for more. Probably a decent deal. I wouldn't let the dust and sitting 20 years scare me off. That's just 20 years less wear on the machines.
Rodney

I don’t think that the 111W151 is a compound feed (walking foot) machine, so they probably aren’t as much in demand as the 111W152 and up (153, 154, 155, 156) are for the most part.

CD in Oklahoma

You'd think they would at least dust off the machines before taking pictures.

Yes, that was my thought too. It certainly would not have taken but a couple of minutes to do that and the return for that work might pay off in a sale.

I have just recently acquired a Singer 111w151 - anybody familiar with them? I have downloaded the manual for the 152 and up - I think the only main difference is the 151 has the needle feed instead of the walking foot. I need to spend some time with it and get to know her. She sews well, but wayyyy toooo fast.

bkvail, this might help, it's an Army parachute repair manual that has info on your model: https://books.google.com/books?id=2P8XAAAAYAAJ
As far as the speed issue, you can replace the old style clutch motor with a servo motor. If you go to Amazon or Ebay and search for "servo sewing motor", you'll see some options in the $100-150 range. You can dial down the speed and control the machine much easier.