I've never seen any advantage in buying used, progressives. People want too much for them and they get bid up way too high on auction sites. You would pretty much have to spend all your time watching CraigsList ready to pounce, since any good deals get snapped up fast, or scour estate sales. Either way it's a huge investment in time and requires luck to find what you want. Plus in a rural area or small town, there's probably not much locally.
With a used progressive you're a) probably not getting one setup the way you want (caliber, etc) and b) unless buying from someone you know and trust, there's no telling what the previous owner screwed up and what parts might be missing. Getting it all restored & setup properly is not a job for a beginner and more time than I want to spend when for a little more money I can get it complete and spend my time reloading instead of tinkering.
In fairness, I have heard you can just about find a Dillon press frame in a junk yard and they'll restore & replace everything free. RCBS also stellar customer service, in my experience.
I guess you could add me to the instant gratification crowd. No, I actually did shop used and came up empty before buying a Hornady AP.
A used single-stage, on the other hand, is likely a great value, especially if purchased from an individual. They have a minimum of moving parts and you'd have to be, uh, pretty special to screw one up.