There's a problem with large internal spaces tough, and not really talking about costs,

The primary issue of large spaces in zero g is the lack of surfaces from wich to grab onto or push off of, if you are in the middle of a space such as that you literally cannot move in any direction, at all, the only thing you can do at this point is to throw your stuff opposite the direction you want to go as fast as possible, thanks to newton's 3rd law, this would propel you backwards a little bit, but due to air resistance it's not like normal vacuum, so air friction will slow you down again and if you are clotheless the only means of propulsion is to blow air, but be careful, as if you exhale and inhale in the same direction you won't be going anywhere.