My buddy had a book store in Oakland with a “hair salon” next door. When the “salon” moved out the landlord did a reno. We were shocked when they started pulling out odd items like jacuzzis from the back room. Turns out the “hair salon” was just a cover and there was a bordello in the back rooms. LOL.
There was one in a city near me a few years back. Hair salon, nail salon, massage, something. Turns out they were running a prostitution op. Very small. Part of that city I never go (like about 90% of that city).
Was out with a friend one night - we weren’t that far away so he showed me where it had been (it was on the local news). Just a small road-side shopping center of about 5-6 businesses (they were busted and closed up by then).