Why do Jehovah's Witnesses Headquarters keep "Buying More Property?"?

It this a "compulsion?" Why do they need such a large physical expansion? Is this a pattern that Jesus would approve of ? Isn't there enough room in a few buildings? Weren't first Century Christians a very "simple" people? is this "numerical increase surpassing ancient Jerusalem? Why do they do this? They are using lots of money aren't they? Who's money?