There is no air in space, and space is usually much colder than the coldest places on Earth. People can live in space, however, if they are inside a spaceship or satellite which provides them with air and keeps them at the right temperature. In addition, people who go into space must bring food and water with them, and have some way of making electricity to power their radios and computers. The longest time that people have spent in space is several months, on board a Russian satellite called Mir. It turns out that one of the hardest parts of living in space is that there is no gravity, and so your muscles have to do almost no work - not even make you stand, because you simply float around. This isn't healthy for muscles or the body in general, and makes returning to Earth (where there is gravity) very painful. People want to try living in space (at least for a few months or a year) for a number of reasons. One is to travel to other planets, such as Mars. Even though Mars is one of the closest planets to the Earth (Venus is also pretty close), it would take a spaceship about a year to get there, and another year to get back. Also, people would like to build large space stations in orbit around the Earth where spaceships could land on their way to other planets or the moon, and this would also require spending alot of time in space. In addition, there are many interesting and important scientific experiments that can only be done in outer space, and the scientists need to be able to spend time there in order to do their experiments. It is also possible to learn a great deal about our planet's environment by observing it from space. All these reasons and many more make people want to live (at least some of the time) in space. But because the zero-gravity conditions are hard on the human body, people need to practice just being in space so that they can stay healthy and do good work there. There would almost certainly be more info on this subject at the NASA web page.

With current technology, we can live in space.A good example is the Mir space-station. It is very expensive to do, however. The reasons why people want to do it aren't always scientific. For some people, it is a status symbol that shows the world how advanced our technology is. For other people, the reasons are scientific; you can do some pretty neat experiments in zero gravity. You can make certain types of chemicals in space that you cannot on earth, for example.

Your question is a very interesting one that has prompted NASA to establish a special division for studying astrobiology. People are able to live in sace for short periods as shown by space missions such as the space shuttle flights and the Russian Mir Space Station. There are problems that occur with trying to live in space because the body is used to having Earth's gravity. Health problems occur when gravity is gone such as circulation problems and loss of muscle and bone mass. While none of these problems have been really severe in astronauts or cosmonauts, nobody has tried staying in space for more than a year and so it's hard to know what the effect of living in space would be on the body. What do you think would happen if a baby were born in space and allowed to grow up in space? Do you think it would survive without gravity? What would happen if it were brought into Earth's gravity?
Living in space often means living in very small spaces with other people for long periods. Psychologically, this can be very difficult for people and astronauts and cosmonauts often complain of irritability when they've been in space for a long time because there isn't very far to go in a small space station or shuttle.
As for why people would want to live in space, a very important reason is overpopulation of the Earth. If the Earth's population continues growing at its current rate, we may have to find more space for people to live either in space or in the oceans. Scientific studies have been tremendously advanced by technology related to the exploration of space.
For this reason, many scientists want to continue studies on space stations such as Mir or the new international space station that is being built. Another reason is that some people are fascinated by the idea of living in space. There is something exciting about getting away to exotic places and there aren't many places more exotic than space!