Yes
Yes, bugs & rats are common in this industry.
Yes and no. After you've been in this business a while, you get desensitized. If I see a stuffed animal covered in rat feces, obviously I wouldn't resell it because someone's kid is going to be snuggling with it. But if I found a box of dishes covered in dead roaches, I'm going to wash them. That's an extra $10-15. If you find an old dresser that you could sell for $75 more if it were painted, you would paint it right? Same thing with cleaning items.
Our business can be disgusting at times. I'm sure no one here likes finding someone's crusty underwear, sex toys or urine in a coffee can, but these are realities in our business. You gotta take the good with the bad.
This.
I wouldn't sell clothing, stuffed animals, etc. that had been soiled* but those are items that are hard (if not impossible) to sterilize. A box of dishes, a statue, a coffee table, etc. can be cleaned and if I would use it, I would sell it to someone else to use.
The fact is, a lot of things get sullied and you never even know it. A rat can crawl across a can of beans that you then use to make chili; a roach can walk over a roll of fabric used to make your bedsheets. Germs and such are all around us, and fortunately, most things can be cleaned.
There's a difference between throwing out a $.25 mug because it isn't worth your time - and tossing out hundreds of dollars of merchandise because you don't believe in the power of Dawn dish soap.
It's up to you what you do, but even bidding carefully and perhaps even just picking at small auctions, garage sales, etc. you may have a very hard time. Most things get dirty, and in some areas rats/mice/roaches may be almost impossible to avoid. Hell, I stored my OWN belongings for a year once while traveling only to find that mice, geckos and scorpions had gotten into them. Was I going to throw out my family photos, furniture and dishes because of that.
Looking at anything in life as black/white with but a few exceptions is going to make life hard. That's doubly so with the auction business.