It's a little hard to believe that you'd be comfortable building your future on something you've only just learned to do, without getting to know the basics of your toolchest to the point that you can even make decisions well.
All I know is that when I've hired, the number of genuinely different languages that someone speaks has been a very strong predictor of whether their code can be kept in the long run.
But sure, picking a language without even knowing what the product will be? That could work too.
I know plenty of amazing devs who do extremely well either as an entrepreneur or as an employee who know none of what you originally suggested. I agree with Sean. He just needs something to start off with.
All I know is that when I've hired, the number of genuinely different languages that someone speaks has been a very strong predictor of whether their code can be kept in the long run.
But sure, picking a language without even knowing what the product will be? That could work too.