Personally, choosing a mini-lathe, in our case an ex-display model, "sold as seen" by Warco, was a matter of risk management. Having researched a little, we knew what problems and limitations we might encounter and the costs in time and money that could be involved. It needed adjustment (particularly the motor mounts – the belt slipped making a noise that caused me to remove the headstock to examine the gears), but once this was done, and some minor adjustments carried out it performs exactly as expected. When I needed to order parts and accessories all it took was a phone call and they were with me the next day. Yes, the speed controller could blow (although given the volume of these machines that are sold, the absence of advertisements for replacements suggests it is unlikely), in which case I would probably be looking for a scooter motor, but there is no guarantee on the motor of a second-hand machine either.
Looking at the number of articles on the web detailing improvements and corrections to the Chinese machines, it is possible to get the impression that they are all at best "kits", but then again, a quick look at the number of articles on Myfords to be found in ME over the last half-century could make you think the same thing. As far as quality is concerned, unsurprisingly the components aren't going to be the best that money can buy (in the Cromwell catalogue an 80mm 3-jaw chuck is more than half the price of a mini-lathe!), but at least they aren't worn out by 20+ years of 40 hour weeks.
Quite apart from the fact that my son wouldn't have got most ex-industrial machines upstairs, for us the risks of purchasing one outweighed the benefits. In most cases the machine cannot be seen (or perhaps more importantly heard) running, and if some of the machines I used in industry were anything to go by, a bed regrind costing more than the mini-lathe might have been the least of our worries. I wonder how many machines we would have needed to look at before finding one that is both cheap and good? Even minor things like missing change gears could add up at more than £10 each. assuming they can be found.
Brian