Maybe homes in the Soul Cairn?
There are building structures and a large black chapel. So we can assume there are places to dwell. If not, they can just chill out at a grave.
I have an evil vampire one that I classify as such who is going to sire a vampire who will be good and he will also join the vampire faction, its very exciting this is not another black and white tale and there is some gray thrown in there.
I am excited too! I have two vampires who see the Dawnguard as evil, and wish to bring about vampiric dominance upon the land, but one of them is still skeptical if the blotting of the sun would be an ethical thing to do.