Jonathan never quite articulates why he decided to become an unlicensed private detective. However, given his girlfriend's reasons for breaking up with him, it seems he was motivated by a desire to be tougher.
White wine is certainly not the kind of drink that most private eyes would drink and helps illustrate why Jonathan is not a Hardboiled Detective.
A large part of Jonathan's problems with not being able to intimidate anyone is due to the fact he doesn't have any sort of weapon like a fictional private eye would. Which is due to New York's strict gun laws and the fact that, well, he's Jonathan.
Given the number of brothers and sisters Jonathan must have for many relationships currently in progress started because the couples had so much in common with each other.
Jonathan keeping the fact he's the biological brother of Rose from her while they engage in a sexual relationship should probably count as rape by deception.
