google it if you want free models. If you want to know how to model a fast basic city, just draw out a city with an aerial view (top of the earth looking down to the grown). Then just draw how your streets will look and where your buildings will be. (Draw different shapes for the buildings, not just a plain box). Scan your drawing in the computer and trace around the difference shapes to make the land and the buildings (Make them seperate objects). Fill the holes in the different objects and select all the faces( Except the faces that makes up the street), and extrude the faces until the buildings are the height that you want off the ground. Texture the buildings any way you want and presto! you have a model of a city.
if you don't want to draw anything before hand, just use google map to get an aerial view of a city.
