Yes. On Mordred or Gaheris, you can have any realm's house in any housing zone. Important: Houses purchased in a market will be of that realm's style. Ie., a cottage purchased in the Albion housing market will always be an Albion cottage, regardless of where it's placed or the purchaser's race. Houses purchased at a cornerstone will always be of the same style as those of the purchaser's realm. Ie., a Lurikeen buys a cottage at his Midgard cornerstone. The cottage will be a Hibernian cottage model.