Funding
Space colonization can roughly be said to be possible when the necessary methods of space colonization become cheap enough (such as space access by cheaper launch systems) to meet the cumulative funds that have been gathered for the purpose. However, there are no immediate prospects for the large amounts of money required for space colonization to be available.
The President's Commission on Implementation of United States Space Exploration Policy suggested that an inducement prize should be established, perhaps by government, for the achievement of space colonization, for example by offering the prize to the first organization to place humans on the Moon and sustain them for a fixed period before they return to Earth.
In addition, funding of research that aims to develop cheaper methods of space colonization also contributes to making it possible.
Read more about this topic: Space Colonization