I don’t think he was a gigolo I think Rosa’s mom blackmailed him. ( probably due to his adopted families company and keeping the fact she most likely killed them ) a secret by bringing him into their home. Under the pretense of being a male Prostitute.
Cause from the flashback he had while with Rosa. It looks like she tricked him, most likely forced him to do those kind of things to her and then blackmailed him into keeping silent. Maybe he found something out about Rosa’s mom.
also this might be far fetched but this further proves my theory that Rosa’s mom brought him into their home for Rosa to toy with. It seems she wants to break him & if that’s the case I feel for Yeonwoo