What about his estate? Try narrowing that down since that could relate to any number of questions regarding that a place, 'cos that's pretty vague.
What's its purpose? How do you get the quest for it? When does Slim Couldry allow you to return? Will it be accessible once you've completed the quest like other places? How do you beat it by taking advantage of the bug? Walkthrough of the place? What are you supposed to steal down there?
And whatever else one can come up with regarding Bann Franderel's Manor. So be specific on your next questions or people like me aren't gonna bother answering. Thus no help for you.
The only thing that can be said with what you have given is you cannot unlock it without the crime wave series of quests.