Before my parents downsized -5 yrs ago - my Mom and I spent days, nights and weekends cleaning out the attic, garage and cellar, just for this very reason.
There was one realtor who brought candles. My mom's realtor told her the house was clean (before any showing/open house everything from ceilings to silver were cleaned) and not to light the candles.
I won't even tell you about several houses MH and I looked at 10 yrs ago. Water (6" at least) in one basement, bundles of papers....