And, there is a bit more to the story. First, there is the fact that some according to some stories, Giuliani asked to be paid $20,000 a day, a fee that would most likely be held to be unreasonable under the rules of professional conduct.
When asked about that story, Giuliani supposedly said that he had not asked for that amount. Instead, he told the New York Times, he had not entered into a formal agreement with Trump but that they would "work it out in the end."
Agreeing to provide legal services without an agreement and expecting to work it out in the end with a client notorious for not paying his bills... well, that's not very smart... which raises the issue of Giuliani's competence, but that is yet another story for another day.