I mean, it must have occurred to Buddy Boy, now and then, what those greaseballs were doing in possibly every room of his apartment, on his couch-- he found a cocktail sword, why not a used condom?-- in his kitchen, his shower, in his bed? there was only one bedroom. And they were all kind of disgusting to begin with. How could he even stand to live there?
shareThat probably occurred to Baxter but he probably over-looked it because he wanted a promotion and he knew that the only way for him to be noticed in the company was to let him bosses use his apartment for their affairs.
It WAS a gross premise...which is why it was a groundbreaking film in a groundbreaking year, Hays Code censored 1960(that also saw Hitchcock's "gross" in a different way, Psycho.)
But there is a love story and a happy ending attached...one 1960 critic called it "a dirty fairy tale."
Regarding what happens in that apartment:
Billy Wilder offered the film to the first actor offered Sheldrake(Paul Douglas, who died of a heart attack just before filming began) by saying:
"I'm making a movie about f-ing. I want you to star."
Wilder said this to Douglas in front of his WIFE, Jan Sterling(the no-good wife in Wilder's "Ace in the Hole.")