Can anyone create or update a page on Wikipedia?

A few blocks away, I have a distant cousin who works as a content writer. She currently works full-time at an advertising agency, but she has always wanted to write material that is based on research because she finds it to be much more enjoyable than writing creative or promotional content. She remarked that she had been considering working for Wikipedia as a writer or editor the last time we went shopping. I was a little taken aback because I had no idea if that was something that people did for a living. Even she was unsure of how Wikipedia operated, but I suppose there are subject matter specialists behind its extensive content. Are there professional Wikipedia page creators available for hire? If so, how are they different than any usual writer?