"What are you" would tend to be taken as an expression that basically asks what somebody's character or personality is like. It could (possibly) sound accusatory, like "What ARE you, man?" Implying that they are a bad person. If you want to ask about somebody's profession, a few phrases you can use are: "What do you do for a living?" "What do you do for work?" "What are you doing for work?" Just FYI, the first phrase has a counterpart expression, "To make a living." i.e. to earn a salary that you use to live. I hope this made sense. Good luck!

The correct way is- What do you do for a living?

No, don’t ask someone ‘what are you’ without more context. Alone that doesn’t refer to a profession. It could, with more of a context, maybe mean that, but I can’t think of a case where that would be so off the top of my head. In fact, to ask that could be easily misunderstood in English, and be rather insulting, and be taken as question about the person’s race, ethnicity or national origin. So be careful. Like, “what are you? Black, White, Asian, some mix?” I would say “So, what do you do for a living?” Or, “Do you have a profession you are in.” You have to be REALLY careful the way that question is asked in English. In German it’s really easy. But, not in English. People in the USA can be VERY offended by a question about what they do for a living, so even the tone of your voice has to be polite and respectful. It’s odd, but true, , at least over here.

Just as a quick addition, the only time you might pose a question similar to the way you phrased it, “What are you” would be if you already knew the person was, say, a physician. You could then ask “Oh, what kind of a physician are you?” That would be okay. But, like I said as a side note, at least in the US, you have to be fairly careful in even asking that question of people because they often aren’t proud of what they do for a living. So, even when you use the correct language, you have to ask it in a nice way.