From Live Letter VI:-

Q: If you buy a small house and piece of land, when it starts to get too cramped will it be possible to upgrade to a larger house?
A: We're working on a system for moving that will be introduced in a patch. Also, depending on lag and stress on the servers, we may allow players to own a second house. But yes, you can be sure that when we're finished, you'll be able to upgrade to a bigger house.

Q: Will it be possible to sell land deeds in the market ward or other places?
A: Yes, it will be possible. They can also be traded. Just as an example, you could give a house to that special someone in your free company as a present.

Q:Is it possible to have multiple houses? For example, to have a primary residence in Limsa Lominsa and a villa in Gridania or Ul'dah?
A: Right, it's just like what I was talking about before. Having a main house with another house located in a different country. Once we have a better understanding of the burden this will place on the servers, we might be able to implement this.