There are many approaches to player owned dwellings. In Ultima Online, you can place a house anywhere on the map, outside of cities and special areas so long as the terrain is flat enough. In games like Mortal Online, you pretty much place houses outside of cities, but only in predetermined areas, so similar to UO but with some restrictions while in DAoC (at least, as far as I remember) there would be a special "map" where players can purchase a house.
In TGOW, players actually own structures within cities. While in most MMORPGs, cities are really just small villages where you can stock up on stuff, or meet other players, in TGOW cities are... well, actual cities. This means that it will have the traditional "commercial district" that most games have, but will also be surrounded by houses players can purchase.
This also means that cities are going to be huge, which introduces a few challenges. (coming soon...)