Hi @Rachael52: How timely this post is. I was about to post on this subject as well. I have, I hope. some helpful information for you. First, if you are not finding mold, chances are that smell is leftover from the mold drying up. It is harmless, but yeah, kind of embarrassing. So many people equate it with not clean when, in fact, you place is very clean. I have a 72 year old home built of extremely old redwood timbers (reclaimed from a train station in fact) and the walls are plaster not drywall. There is no mold in the house, we have checked and rechecked, I work my butt off trying to get rid of that odor. Most of my guests have no issue with it, they are generally of an age that they understand that older homes in a foggy coastal area have an “old house smell” and they are fine with that. They can see the house is clean. It is the uneducated early 20 something females that I have issues with. No offense if any are hosts here please. But they seem to think they know just everything about why things are they way they are and they are just going to educate you right now AND punish you for not being perfect by giving you a not so great review. Who cares that they are messing with someone’s income.
In my research I ran across this information on the Realtor.com site https://www.realtor.com/advice/home-improvement/old-house-smell-removal-whats-causing-get-rid/
I have already done most of it but I am going to try their cleaning solution on the walls. I will post to its effectiveness but it won’t be for a day or two. Here is the wall cleaner “recipe”. I have found it numerous places other than this site, so I am hoping that means it is effective.
½ gallon hot water
½ cup borax
2 cups distilled white vinegar
16 ounces of hydrogen peroxide
Right away, wipe down your walls and let them air dry. This will remove grease, dust, and mildew, and also remove smells that have embedded into wall surfaces or wallpaper,
I hope this helps. Good Luck!