question about blender and modeling

question about blender and modeling

I have never modeled before and was wondering a few things. How often are models to scale. Like if you were going to build a tavern and a knight in armor would you figure out the size of the tavern based on real dimensions or just start pulling polys until you have a model and resize it later. Wouldnt it be annoying if a game company had to resize every one of your models seperately in game. Do most people just create a model without concerns of real dimensions or scale.

Also is there such a thing as what I would refer as a "dirty model". Maybe a model that was clearly done by an amature. What would make it dirty or why would it be considered a crappy model.