> Colonizing mars is not so easy to show as feasible. Certainly we can launch a bunch of cans and digging equipment and get a few people living there. But anything like a self sustaining population? Don't know, we don't really have a concrete plan of how to do that.

Elon Musk doesn't have a concrete plan for a "self-sustaining population". I think all he is actually planning on doing in the medium term is working with NASA to establish a research station with a few dozen people, devoted to research into how to live on Mars. The research station is going to be dependent on continual resupply and funding from Earth.

Growing to the point of being a self-sustaining colony capable of surviving without continual support from Earth is likely to be many centuries away. However, I think Musk is going to want to call it a "colony" from the start, because of the power of aspirational naming, to centre the hope that it will grow into that. But even if it eventually gets there, none of us are going to live to see it. And there's no point trying to even come up with a detailed plan – for a multi-century project, the only possible plan is to make it up as we go along.

What is Elon Musk going to do with his immense wealth when he dies? Don't be surprised if he leaves a massive chunk of it to a charitable foundation devoted to paying for the settlement of Mars. Absent a new Space Race (which may yet happen at some point), governments are unlikely to want to pay for anything more than a few research stations, but ultra-wealthy private benefactors may be willing to pay for a lot more.