I certainly agree with the player being able to own houses. Building houses seems a bit iffy to me though. A small log shack can be made in a day or two, but large structures, like castles would really take much too long if we were to keep any semblance of realism, and there would be no way you would be able to construct stuff like that alone. The best implementation would be perhaps to allow the player to start a homestead with a little shack if they're the loner type, or, if you've massed up a lot of followers, or have the wealth to hire a lot of workers, larger structures could be done. Another problem is gathering the resources. Would the player chop down a tree and get a predetermined amount of 'wood' points, or would the actual length and girth of the resulting log be taken into account during construction? And then we have the stone for a castle. You're gonna need a quarry, and workers to work in that quarry if you ever plan on achieving more than a small tower, IMO.
And then, farming. This idea seems a little iffy, to me. If we continue the semblance of realism, farms will need to be maintained. Not a problem if you're a lord with peasants under your belt, but if you're the aforementioned loner type, nobody is going to watch your crops for you while you're out slaying trolls miles away from civilization. Someone might steal your crops, or destroy them if you have enemies. Animals could ravage your fields, or your crops could get some sort of disease that require attention. I don't really know if BM is going for levels of realism that extremely high, but I don't want to see 'hit mountain side with pickaxe for 2 hours, build grand castle' or 'Throw seeds on dirt, ignore it for 4 hours while crops that the god of farming envies grow in your absence."