You have it backwards. Mars is a deep gravity well that adds huge energy costs to both landing and return trips. You don't want to build anything on Mars. Aster

You have it backwards. Mars is a deep gravity well that adds huge energy costs to both landing and return trips. You don't want to build anything on Mars. Asteroids are much less costly to reach, offer better living environments and far more resources. You want to build out a few asteroids with fuel depots, ship construction/maintenance equipment, and mine cheap extra delta V to spend on mars.