DIY future basement sauna

In the permitting phase of building our dream home and had a spot set aside for a sauna to be built in the next few years. Just started reading through the treasure trove of info on this subreddit but had a few basic questions related to the base house going up.

  1. Reading through a few posts but it seems the floor drain would not be necessary?
  2. There is drywalls being installed over the concrete foundation, would it make more sense to leave it bare concrete?
  3. Same question for the floor, assuming I'd build right on top of the concrete
  4. 240v seems to be the best option for power source?
  5. Seems for ventilation most systems are designed to intake/outtake into the room it's installed in. Given how humid the air can get, does this pose any issues for the house itself? Bathrooms typically vent moisture out of the room. Just wondering if I should spec the outlet vent to go outdoors as it's a simple matter at this point.

https://preview.redd.it/lgkox76zfr5c1.png?width=250&format=png&auto=webp&s=48e50fced63c472c90a4d7b2d9a0e4bed5aa0bd7