The International Space Station usually accommodates 6 astronauts at a time for a period of months. If we have other habitats in space, I don't know about them, but at least one company has a contest operating right now for designing moon and Mars habitats; and Google LunarX Prize had some moon landers ready to launch in 2013 and will proceed in 2015.
In the 1990s, a group of doctors in Ohio was ready to attempt building a cardiac clinic on the moon, but that did not happen.
Since no matter how much exercise we do in space, we still lose bone and muscle mass, while the heart loses so much mass it becomes smaller and spherical, I think we have much time to wait for a habitat out there that will keep us alive.
The Dutch group plans a reality show to select people from many astronauts in training to colonize Mars sometime between 2018 - 2023, but that might be wishful thinking. NASA's current group of astronauts chosen in 2013 are planned to travel to Mars about the same time or a few years later, but not yet to stay there.