This exercise is very difficult, because there aren't very good popular information. There is one page of the NASA, http://sapceflight.nasa.goy, but it's necessary a lot of time to search the information.
Now, after one hour in search of, I can say: Un astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft.
I don’t now how long does it take to put on a space suit, and they salary is, more or less, 4.500 € to month.
It’s possible have 25 years old to be an astronaut, because the youngster has this age.
In a space is possible to see stars and the Earth, this isn’t difficult to now. And, finally, I don’t now how they do sleep in a space.