In Epiphany, when Angel goes to save Cordelia from the three eyed demons, was the mother of the family already killed?  Because Angel crashes right through the house in the truck without being invited.  Did I just miss that part?

Just saw that ep last week, I think.  After the mother calls Cordelia, the demon snaps her neck.

Mm, okay.  On a related note, I wonder how demolished a residence has to be in order not to be considered a residence?  I'm not sure this ever came up in the show.  But like if a house burned halfway down, could a vampire enter the ruins, you think?  Immediately afterward, or only after the people said, "well, we can't stay here tonight."

Well, if the house was partly in ruins, probably no one would be still living there, so yeah, the vampire could go in. Unless you're talking about the vampire going in while the house was still burning... which I'd say is a bad idea from the start, given that vampires are highly flammable. I'd say in that case, they couldn't go in, since it wouldn't be considered "abandoned" yet. Not until the people who lived there decided they were never coming back.

I like your explanation, Eowyn.  It also explains why Spike can enter the house in Touched.  Obviously, that guy wasn't planning on coming back!