The title of Fading Gigolo actually suggests a theme that I don't think is the central/emotional part of the story.
Never-married Fioravante (John Turturro, who also wrote and directed this), aptly named because he is a florist (it means something like "first flower"), is talking to his older friend Murray (Woody Allen, who also contributed some to the comedic writing), a bookseller who is closing up shop due to the financial climate. Murray tells him of a conversation he had with his dermatologist (Sharon Stone) where she expressed an interest in a three-way sexual tryst with her and her attractive friend (Sofia Vergara), and did he know anyone who would like to do this? Murray suggested Fioravante and while Fioravante initially balks at this idea, is intrigued enough to do it. But the dermatologist wants to try Fioravante out first on her own, so he goes to her lavish apartment where we find she is in a loveless marriage, and seduces her, we see in essence she is a "desperate housewife."
This becomes pretty successful and for a time Fioravante and Murray gather other clients, taking them to Fioravante's apartment in the (I think) Brooklyn area. Murray meets a young Jewish widow/mother Avigal (Vanessa Paradis) and her predicament is that due to the restrictive elements placed on women in her orthodox Hasidic religion, she is very lonely and needs human interaction, both emotional and physical. She decides to visit Fioravante more as a therapy than for sex. They talk and he touches her and gives her a massage. An old friend of hers, Dovi (Liev Schrieber) who works for a Jewish neighborhood watch group (they are almost like local police for this Jewish community), presses her to get married to him now she has been widowed a while. When he tails Avigal to Fioravante's place, he gets jealous even though he doesn't know what's going on there.
Meanwhile, the dermatologist is working up the nerve to finally do the threesome, but by that time Fioravante's attraction to his new job has lessened due to Avigal's presence in his life.