What guilds do you accept when they offer?

[WhiskeyGhost]

What does masons do? Cheaper building in this city or everywhere? Are there other bonuses?
(If not, it looks useless to build a lot in one city, to get discount on what WILL be built there when almost everything is already finished)

First level gives a 30% building discount in the city it's built in. Second level gives that bonus, and a 20% discount in ALL other towns/castles. Third level gives 30% locally and to all other towns/castles if i recall it correctly. Thats a sizable discount if you can get it early on, but most of the time, you could easily afford to upgrade all key locations without the discount.