If it was me, I wouldn't buy them. Tires have special compounds in them that keep them "pliable" and when you let them sit too long, as in years, the compounds can't do their job. They might look fine sitting there, but as soon as they are mounted they could show signs of dry rotting and cracking. Overall the tire can degrade as well. Especially watch out if they have/had them sitting on one of those racks that sits outside in the sun
-Nick