hehe, each building will have its own function, 6 buildings for recruting 6 different monsters, 1 building for learning spells, level 1 to level 5 spells, that means the building can be upgraded 4 times.
1 building for buying armour and weapons,
1 "city hall" building, that can be upgraded 2 times(the function of this building is how much tax money that is collected each week, when upgraded u get more money)
and finally 1 garrison building, where u can buy all 6 monsters from.
phew!
:-)
Note that upgraded buildings dont have to differ much in style from the ones you start with.