[devs1010]

Not this. Even if you want to do mobile apps, just starting out you need to work with other developers as you learn a lot from them. If your goal from day 1 is to work solo you aren't going to have that feedback loop where you are pushed by your peers and can learn from your (and their) mistakes. This is compounded by the fact that you will probably develop proficiency working solo to where you can do things well enough to make money, but the customer doesn't know software design patterns, writing maintainable code, etc, they just know whether something specific works or not. Overall, without working with others I feel a career can stagnate. Its a bit of a cliche, but a lot of developer bloggers write about how if you aren't working with people smarter than yourself than you need to find a new job, by always working solo you're missing out on this entirely.

[axefrog]

This is absolutely true. I've worked both solo and in small teams many times and whenever I've worked with others (particularly senior developers) who had decent skills I always learned a lot. When you work by yourself you don't have the benefit of other people to bounce your code off of, or of being exposed to various techniques, methodologies and tools you may not have discovered if left to your own devices.