Yeah, that was my thought too. Diana always had contacts and resources way out what a woman in her position normally has. I bet she has a nice little trust found or that the apartment was a nice little Christmas present - who knows.
And she talks about it in "Need to Know", Season two, episode two. Still my favourite episode of the whole show which isn't a mid-season or season finale or season premiere.

I wonder if Neal really wants to go back to criminal life...when he first talked about "being back" and "cutting all his strings" it sounded that way, but now I have the feeling that he plans to cut his strings and then show everyone that he is able to toe the line, no matter what they think. Searching for the diamond is in itself not illegal after all. If he and Mozzie find it and opt to make the find public instead of selling it on the black market, they could life in riches for the rest of their life, perfectly legal.