I do think some form of shared housing is kind of nice, as it can make a really good starting point for new characters to build CR.

I also do think some kind of event setup to introduce the change would be a good idea, whether it be fixing up the mansion/establishing communication/etc. or not. It's not gonna be a seamless change either way, so rolling it in with a bit of a bang might work better? So I would not be opposed to the mansion being a spoopy mysterious fixer-upper kind of thing, per se. It makes a nice chance for a sort of event-like ongoing thing for characters who aren't necessarily super action-oriented.