Going to be some very expensive gas.
"Apollo samples typically showed helium-3 concentrations measured in parts per billion. That means enormous volumes of regolith must be processed to extract useful gas. The basic industrial recipe is straightforward on paper. "
Lunarians can never go back to Earth because their bones will be so weak…
If the industrial base is there you could build an angled gyroscope to add the necessary gravity. Although realistically much of the processing and shipping would be automated anyway. Unless AI gets really good some humans would still be necessary for oversight but reasonably with only a couple of seconds time delay that could be done from Earth.
If we were doing asteroid mining out in the belt that would definitely require some sort of habitat though. Again, assuming we don’t get AGI or uploading humans to software or something like that.
Yet another reason we’ll never move into space. That’s where Bio of a Space Tyrant gets it right. Humans are able to harness gravity and make it variable. If we could do that, 95% of solar system exploration issues are magically gone.