Normally, we do not put a preposition at the end of the question when we use the interrogative pronoun "where."
Where are you going? -- not Where are you going to?
Where did you stay? -- not Where did you stay in?
Compare this with when you change the interrogative pronoun to "what" or "which":
Which restaurant are you going to?
What hotel did you stay in?
*Note: There are of course exceptions to this like when we ask "Where are you from?"
Adding the preposition "at" in the question "*Where are __ at?*" is unnecessary and informal usage. It strongly implies casualness and may thus be inappropriate for a business/ professional setting.
Like what you predicted, some people can also connect it to urban slang and you should consider whether such a thing is undesirable for your advertisement. Take the entire context and your exact purpose into account.
Since the questions are asking about "employers" and "entrepreneurs," personally I interpreted is as coming from a dire need for more employment and self-starting entrepreneurs. That's how the language came across to me. It reminded me of an article from Times magazine.
I don't think everyone will get the same message though, whether it was an accurate interpretation or not.