One of my friends from high school is a freelance dancer in SF. I'm amazing by what those girls are capable of. It takes so much determination to keep going.
Most girls can't make a living on dancing itself, so they have to have to find side jobs. Since there's almost no monetary incentive, they do it mainly for the love of the craft.
It's physically demanding because they're often in the studio for the entire day, and they have to be careful to avoid injury. It's emotionally demanding because they have to put themselves in the abstract mindset of choreographers and directors, who they may not agree with.
These girls are fearless. I'd compare it with being a software consultant, but without the pay and flexibility.