You can't sell the house to ''no-one''. If you sell [you fix the price] / donate [free] your house to anybody then the region also does not belong to you, afterwards. Get the money first, then buy the manor or the castle, ok?
Mad at dimos? It has nothing to do with dimos... It's about me, the moderator side of dimos... Imagine a world like you want to have it... all people would have build houses and sit behind walls. Such a game will never end. If you can buy continuously houses, then I can buy continuously armors... But is that realistic? Do you live in many houses? and can I wear 2 tons of armor? Please man, see your mistake... Your boat is at A28 rectangle btw, since that is the ''Dimohill docks''
PS/ EDIT: Imagine a place with 2 castes and a player there with all the armors bought twice. Castles= +6 and armors +18. Max attack 5. Total defence 18+6=24. It would require 5 people to attack him/her and still cause him -1 damage. It does not work that way. You're allowed to have 1 type of anything, even if it can also be unfair that way, for the attacker.