watermilling

Being new to this site and fairly new to civilization I recently came upon the empire management link, and then into balancing economy and warfare. I read that page, and was interested in trying the strategy suggested there. There it was suggested that you build watermills as fast as possible in as many spots as possible, because they are industrial powerhouses, and get food, hammers, and commerce added on later in the game.

This brings me to my question:
When building watermills like this, should I immediately build them or should I wait until state property, replaceable parts, and electricity are acquired?

This question has nothing to do with Civilization Revolution. Please post in the correct forum; Colonization?

Civ IV not colonization or revolution