We've been having our new house remodelled. One thing that really surprised me is how impermanent the walls are.
I've always thought of the walls of a house as fixed objects, invariant constraints you work around. But all it takes is a crowbar to open them up. Then you can run wires through them, put in plumbing, ventilation. We even moved a wall a couple of inches to steal space from a closet and make the kitchen larger. No big deal, assuming you have a good drywall guy to finish the job.