There's a lot of factors to consider when buying used. If it's a brand new, lightly used, never crashed model, I'd be concerned about the conditions it was stored in. A lot of people will decommission models to their garage or basement. Sometimes those are high humidity areas and will create surface rust on the bearings and other components.
If you just want a quick fix, put a drop or two of light oil on EVERY bearing and spin it by hand before powering it up again. Apply more as you see or "hear" fit. I would also take apart the head and grease the thrust bearings and give a good inspection.
I personally would treat any used model as new, follow the manual, and completely disassemble and reassemble it... Cleaning and lubing as I go. There could be stripped screws, bolts, nuts, lack of loc-tite, CA, grease, etc.. If anything is questionable, take the money saved from purchasing used and put it towards any new parts that may have been neglected.
It's best to familiarize yourself completely with every part on the model for future reference. Flying machines require more maintenance and more frequent checkups than surface vehicles, so knowing what the assembly is like will help in the long run.
Hope that helps!
edit: Please note: WD40 / PB Blaster and other similar common products are not lubricants. They are degreasers and rust removers. If you use them to break up rust or degrease, you will still need to put an actual lubricant on the components afterwards.
