There are already a bunch of people here on earth that "work to live". It is called "not starving".
I think most of you guys really don't understand the timescales here. The people in the missions in the first few launch windows would have to be stuck in those harsh prison like conditions for a decade or two before their day to day could even begin to resemble their life on earth. This "sense of exploration and adventure" would really die out after a few years when you realize you haven't really explored anything in the past year, and that all you really do is fix machines and try not to die.
Sure, the first launch window or two would be exciting, with people signing up to be the first, to be in the history books, to be famous. But after a few "mishaps" kill some people and the reality shows about Mars end up showing the true reality about what it actually means to live there(it is not a vacation), the desire to go will really drop.
Not a lot of people have 200 thousand bucks and the desire to risk death, abandoning everybody they know in order to go live in a prison just for "the sense of wonder and exploration". A ton of people would say they want to(I'm looking at you guys too), but when confronted by the reality they would back down.
All the replies here have valid points, but most of them evaporate when you realize we are talking about decades, not years. Anybody can stay a year without seeing their friends/family, or doing X or Y, but try a decade(or 3) without X or Y or Z ... etc. Most people would go nuts, and I doubt 10% of them would still want to stay after so long, even thought they might not regret going in the first place.
I believe a colony with a few thousand people is certainly possible, but for a self sustaining 1 million people colony to happen... I'm not sure what would have to happen to allow that. I guess only something like finding a big gold mine on Mars would do the trick, with people actually being paid to go there or something. Or Mars becoming this big vacation colony, with most people living there to tend to the tourists, which would only make sense if the trip cost was reduced even further.
And comparing this to people moving to America after it was discovered is nonsense, There was an economical reason to send people there, and your life after the trip had the potential of being better.