As far as I know, it is not technically against any official game rules as long as RMT is not involved but SE and most of the player community frown on those who do it for gil. SE did not intend for houses to be resold by players.

Instead of selling it, my suggestion would be to give the FC leadership to someone you know that wants to start a FC. That's what I did in a similar situation. I'm still part of the FC but my friend is a much better FC leader than I would have been.