Anyone bought used rig with musty smells or dog odors?

No, I would not buy one that smelled moldy or had a strong pet odor but if you have to go that route, you can get ODOR-CON from a pet supply. The original use of this product was in swine barns. It's a spray on product. It kills the bacteria causing the odor on any surface and will soak into wood and carpet to get to the problem.

I used that in our house when we raised puppies - made the vinyl floors sticky when I sprayed but water would wipe it right up. I could use it on carpet without any problem. It's clear and smells clean when you apply it. It comes ready to use or in concentrate. You spray it and the odor is gone.

I've done a quick look online and I don't see it. Maybe you can check at your local feed supply / livestock / farm store for it. It's been 10 years since I bought it.

For dog or cat urine...if you can smell it you will likely have to replace the upholstery, carpet and possibly the sub floor.

Our friends bought a house and decided the carpets would need replacing but did not expect to replace all the subfloor. Wood soaks up urine. Not only the floors and upholstery could be damaged but check the woodwork. Dogs lift their legs and cats spray, LOL

I could tell of a case where the insurance company wrote off a motor home due to extensive damage from urine. The cost of repair was unbelievable.

Why would you even consider the unit?

I would say changing the carpet and furniture should take care of it.

There seem to be a lot of people who have bought used, so there must be something that they have done to rid these odors...or did they all happen to luck up on non-smelly ones?

One reason why we wouldn't buy used. You are talking about a small area that traps a lot of odors and does not have the chance of getting properly aired out. They get used very little and are closed up tight most of the time. Some people don't dump tanks the best way and you can get a build up there. People cook different things inside. Many will attest to only cooking inside. WE are the opposite. If we can cook outside, then we do. Very seldom will we cook anything inside and when we do, we try to make sure it's not anything that stinks and we run the fan. Also, look around at the inside of cmapers. A lot of fabric. Most of the time, people don't clean carpets or upholstry like you do in a house. Lots of different reasons. But when we were looking several years ago for the TT we were getting then, we went in only a handful of used ones before deciding to buy new. Yes we spent more on it, but it was worth it to us. Earlier this year, we purchased a used pop up to use in the mountains while the TT we had was stored at the beach. One of the worse smells ever, moth balls. Aired it out several days and scrubbed the inside. The smell was still there somewhat. Never used it. Traded it and the TT in on a brand new Class C. No bad smells there. lol