Mold has a distinct odor. If you have been in a home that has mold you’re probably familiar with the odor I’m talking about.
If you smell it, it’s there! If you suspect a home has mold, explain to the owner of the home they might have it. If you don’t have a nose for it, train it.
Have them contact a licensed mold specialist. For liability reasons, don’t mess with it. Leave it to those trained and licensed for this. It is most dangerous when air born.