What is a registered sex worker? Registered with whom? Or is this a registered business that just happens to be a sex worker.
In any case, a sign on the door that says something like “This foyer is monitored by video cameras. Please let us know by emailing this address or texting this number that you don’t want to appear on our “Visitors” Facebook page” might do the trick.
It’s a sad fact of apartment life that drug dealers and prostitutes like the security that unit blocks offer. However, prostitution isn’t illegal in most states (whereas drug dealing is).
By all means, install actual security cameras – not just to deter the sex workers’ clients. Apart from that, unless there was some tangible sign that this “sole operator” was doing any harm, I’d be tempted to just let it be.
Given that many people work from home these days, you might find the residential zoning isn’t that helpful