LOL. Me, too. A cave is probably a pretty low rent way. Unless you have to carry down a bunch of rebar and concrete with environmental HVAC and sealed toilets and on and on. Then it gets to be a drag, I’m sure.
Ive seen this movie,it doesnt end well.
Speaking of saving money, and time, why in the first place? We won’t even be capable for another several hundred years to do what they are practicing for here. We will have forgotten everything learned by this exercise before then and it will have to be done all over again at the last minute anyhow.