dennisgorelik is correct, and you are wrong, as to a specific scenario which I would still consider to be a "housing transaction". It is 100% legal to discriminate on the basis of race, sex, or any other characteristic at all when choosing a roommate (a special form of renting out your property). It is 100% illegal to place advertisements indicating that you will reject roommates based on race, sex, or other protected characteristic. So in that case, the law is very specifically about the contents of the advertisement, not about the behavior of discriminating against certain renters.