A programmer of course.
Low entry barriers: I know a lot of people learn how to program from other professions. When I lay in college, my major was mechanical engineering. Some talented programmers from Vietnamese major, from constructional engineering major, English major and so on. I learn how to program from 1992, when I was 13 years old. And I met some 13~17 years old very cool programmer, they are very clever kids and know a lot of stuff.
Low material needs: Computer was very expensive before. But now even in China, almost every citizen gets one or more computer in the house. You do not have the required any land, money, any materials, only use your mind, the computer and the internet connection, you can make money wherever you are.
Long career: If you want, you can keep your career as long as possible.
A lot of needs: The world is rapidly changing. Everything will be connected to the internet. There are a lot of needs of programmers.