True...

Some building stats I was looking at show that build an Inn gives you an attract mercenary 'rating' of 40 (whatever that means..) And building a fort has a Mercenary attraction of -10 (it gets worse for Keeps, Castles, etc..)

The Constables palace increases the Mercenary Attraction rating.... But I don't know about anything else, and I only saw it once of a flash version of the tech tree, so I don't even know if it is correct...