How feasible is a career change to Android/mobile app development?

I’ve posted recently about careers that would be suitable and viable for people who recently decided against law school, but am now considering learning JAVA and Android mobile app development. How viable would this be as a career for someone with fairly minimal tech background, but who has the drive to learn how to do it? Is this viable as a long-term career—i.e., is the kind of thing where there will be a huge bubble and you’ll never be competitive unless you’re an experienced developer, or could this be a good opportunity to learn software development. More importantly, how do you get started—is it possible to learn on your own, and how much time would it take to do so?