Hola Ramon - the valour increase is only for units trained in that building. For example, "Master Bowyer" gives +1 to your archers, Xbows etc. The buildings for agents (drinking den+, brothel+ etc) give you extra valour (stars) for your assassins and spies, but not your troops. But the agents' buildings do help keep your province happy and loyal.

Some units needs two buidlings, eg Ghulam cav needs guild level spears and horse guild, and I'm not sure which Master building gives the valour bonus, but the answer is probably on this forum somewhere.