if the first floor of the structure has the appropiate footings and can bear the weight they would save on having to pour new footings by going out. This is really way to big of a question to ask without knowing specifics. But tearing an existing roof off a structure so small would be relativly simple. It could be very similar in price but I would guess up would be cheaper. Plumbing and electrical is easier to run up and down then out. And no new footings so you loose the concrete guys bill.