For main role from middle class ? Are we living in fairytale ??
Of course for main role the dancer must be at least from upper-middle class.

Their apartment looked small, but could be expensive. If she went to school to learn how to dance, that would have also been costly. I doubt they could be considered poor by any sense. Riding on public transit doesn't make someone poor. I also don't see why it matters. I wouldn't like any characters less based on their income.