While this may seem a little backwards, in my experience, one of the best things management can do to defend against a housing discrimination complaint is to plan BEFORE any complaint gets filed.  You might ask:  how can I plan to defend against allegations I have not even seen or thought about?
Fair point.  But, training our employees to follow the Fair Housing Act (FHA), ensuring written documentation is in every file, appropriately responding to reasonable accommodation/modification requests as well as ensuring the community rules are followed across the board can make a real difference regardless of whatever the specific allegations in a complaint might be.  Remember, in many fair housing cases, the fact is that management must prove our innocence.  One of the best ways to do that is to have good records to provide to the investigator.  We then credibly prove the allegations in the complaint just did not happen.  At a minimum, we can show policies in place to prevent discrimination.
A recent case from the Ninth Circuit in California reaffirmed that in a related fact pattern (the facts involved alleged employment discrimination) the defense of any discrimination case starts with implemented policies, practices, and recordkeeping done long before any complaint is filed.  Good advice we all should follow.
Just A Thought.