If you want to have people going there to Mars,
first accomplish the space escalator. On Earth.
Then there is your guarantee of going back with rewards (of resource)
everyone who goes there becomes rich.
Because it becomes accessible.
But. My thoughts now are that, even mining, can mostly
be automated.
May not need so many people.
So underground dwelling. It still needs doors, supporting structures
from within. Where to get the materials for this? Mining.
So unless there is whole lot of people going,
I think the 2nd photo out the 4 (temporary base) is just fine.
Unless to use the mountain itself. They won't need extra support
due to its density.
But that would be limited to a specific location.
I wanted to save you money. So to accommodate many people with minimal
resource. Maybe it is still cost-effective as compared to
these temporary base from the second photo on the right,
if you bring in materials from Earth, ready-made. Even substituting
with plastic in areas. Then far larger spaces in complete safety
of the radiation. (In this sense it is worth it)
But again up to you Mr Musk.
Starting from the 3rd step.
Technology for refining natural resource from Mars,
goes in hand-to-hand with terraformation. As those materials will
be used to create something (not just constructing buildings)
something as sophisticated as lasers creating the magnetosphere sent
to the orbit could be the goal, or something that creates oxygen/water,
etc....... (in mass scale)........
So... first colony, must build a civilization that can accommodate
people who are willing to go there and create these things......
My opinion.....