As long as he’s not acting like a complete arsehole, it’s frankly none of their damn business. They can be nervous on their own time and keep it to themselves.

(Along with other sexist/racist beliefs.) Anyway, he’s not self-invited; he was invited by a tenant, whose judgement you presumably trust enough to want to rent to her/him in the first place.

In short: as long as my tenant is paying, and no one in the apartment is doing anything illegal or destructive, I really don’t want to know who’s boinking whom.