I personally think it makes sense for SpaceX to offer to take over Tiangong I, the Chinese space station that's going to be deorbited soon. It's older and not suitable for safe habitation anymore. If SpaceX could use their launch capacity to bring up fuel tanks and to boost the orbit, it could do well as an orbiting fueling station.

Just launch tankers and fill up tanks on Tiangong and then the space craft with passengers would just have one trip to the space station to fuel up and then go to Mars.

China is going to throw away the station anyway, so might as well give it (or lease it) to SpaceX for a good price in exchange for at-cost refueling for their own ambitions.