He won’t put anyone living on Mars. And even if he did, they wouldn’t last that long.
https://defector.com/neither-elon-musk-nor-anybody-else-will...
https://defector.com/neither-elon-musk-nor-anybody-else-will...
All your other solutions are hand-wavey. Sure, let’s “just live underground” as if that’s just as easy as pitching a tent. And who on Earth is surviving nine months without any food? You’re talking as if Mars is just turning right on Albuquerque.