It depends. They get a lot of money. It depends on what they design and how much the worker pays them to design it!
If they did not their drawings would be the same size as the structure that they are building which would make it impossible to work with them!
Arcitects plan houses, basically, they build the house from the ground up. From that very first brick, you could be messing up. Be an Arcitect and you may suceed your dream of Builing the greatest houses in the world. I recommend looking up Micheal Renolds. He is a great Arcitect... He builds houses out of recycled goods!