Purchasing used records is problematic.  The reason being that the vinyl LP record is easily damaged by poor handling, imprpoper storage, prolonged exposure to the air, heat, playings on inferior equipment and playings on worn and or maladjusted equipment.
   Unfortunately I have found the descripton of the disc condition by sellers far from accurate.  This is not entirely easy for sellers.  Obviously if a disc has deep visible scratches and the seller says the disc is mint or near mint then the seller is a liar.  However fine deep groove dust is impossible to see with the naked eye.  Worn grooves often take an experienced eye to discern.  Not all sellers are experinced LP collectors with access to exemplary equipment.
   For good results the LP always demanded superior and expensive equipment, that had to be expertly set up and maintained.  Storage had to obsessional also.  Is it small wonder the compact cassette and especially the CD became quickly popular?
   Few sellers have the time to play the LP discs they offer.  If they did, I suspect even fewer have access to exemplary well set up and maitained turntables.  So if they did play them, they might well do harm in the process.  It would be helpful when sellers know the source of the disc that they gave a description of the original owners playback equipment.  The only source of reliable used LP discs I have found has come from a nephew who has been selling his late uncle's recordings and equipment.  The equipment he had for sale told me this late collector likley knew what he was about.  Every LP purchased from that source has been as good as any in my personal collection.  Sellers that have the knowledge to put together first class playback equipment should, and if possible at least spot check their offerings.  Under no circumstances should they play discs on inferior or improperly set up equipment.  Optimal circumstances are seldom likely to exist in practice.  The result is that purchasing used LP discs will always be a chancy business.
   How should the collector care for his discs?  First only touch the rim and label never the playing surfaces.  Only leave the records out of their jackets when being played.  Always use an inner sleeve.  The opening of the sleeve should always be inserted into the jacket so that its opening is at a right angle to the jacket opening.
   Always use first class equipment.  I personally favor the best equipment from the golden age of the LP.  I find many modern turntables rather over wrought.  Many modern designers focus on one problem or two, to the exclusion of others.  LP reproduction at its best is always the sum of comprimises.  Personally I feel these were best understood and balanced in the glory days of the LP.  A good modern cartridge however is highly reccomended.  Make sure the stylus is not worn.  The turntable should be set up for optimal tracking weight of the cartridge selected.  The pick up needs adjusting for minimum tracking error and correct vertical and lateral tracking angles.  If the arm provides for lateral balance adjustment, then this should also be correctly adjusted.  If there is a means of compensating for inswing, this also needs to be adjusted correctly.  The whole turntable needs to be on a firm surface, and levelled in the vertical and horizontal plains.
  Beware of wet cleaning methods. Unless you own a well tested expensive system, with powerful vaccuum, you will cause the dust to seat even deeper in the groove and increase noise. I use a swipe with a Hunts brush, and always use the Cecil E. Watts Dust Bug while playing.  Mr Watts' Dust Bug, in my opinion is quite the best device ever invented for keeping discs noise free.
   Enjoy the music!