It’s not even just the obvious plumbing providing hot and cold water, and the drain pipes carrying away waste water. You also need vent stacks for all the drain

It’s not even just the obvious plumbing providing hot and cold water, and the drain pipes carrying away waste water. You also need vent stacks for all the drains. You also need to put in a whole lot of hot water heaters and the associated electrical work to handle their demands.