Using payscale.com, salaries for veterinarians range from $50,000 to $80,000/year for different lengths of experience; combined with the fact that Oscar has always been portrayed as a failing and unsuccessful snack-company owner(with crazy flavours that almost nobody likes) who has yet to break into the local & regional markets, nevermind the national or international markets...I think that it's pretty much assumed to be a given by the audience that Trudy is the money-maker of the Proud family.