Originally posted by jatrax
"Fog" can be many things particularly if the seller is not familiar with lenses.
Yep. Who knows what the seller thought.
Jatrax listed the concerns well. Many of those things cannot be repaired at a reasonable cost, but some might be a cheap fix. Though, as an amateur, I wouldnt try "fixing" a lens myself.
Maybe if you post a photo here. And tell us which lens it is, maybe we can estimate a repair cost. But unless you get this lens super cheap (as in, practically free), it might be best to look for one in better condition. If the "fog" is a fungus, its better not to touch it, unless you know what you are doing.