The only source that comes to my head at the moment is GamerEscape's interview with Yoshi-P here.

He mentions:

GE: There has been talk about free company housing, how will you determine who can access the house or who can change elements of the house? Is that something that is limited to Free Companies, or is this something you can share with friends?

Yoshida: The housing system will have its own separate UI widget, which will have all of your options. It will have access options, where you can say: allow only Free Company access, or Free Companies and those free companies we have made alliances with, or we want anyone to be able to come in, or we want no one to be able to come in. That type of customization will be there to support the housing system. Of course, Free Companies will also have their own chests, where you can put loot and money.
So it seems to be a thing, but no details about how it works.