It all depends on what you want to write. As a professional writer, I started off in creative non-fiction and moved to copywriting, then into freelance writing for in real estate, finance, and job ads. I decided I wanted a Masters and became a fiction writer and then went into IT writing/editing/content management.
As you develop your craft and gain more experience through writing and sending your work into the world by whatever means, you'll start to gain access to all different fields and meet all sorts of people along the way. Let your writing do the networking for you. The better you become and the more people you touch with your writing, the more people will start to come to you.
That's not to say you shouldn't look for opportunities. There are great writing communities all over the world. See what's in your neighbourhood, colleges and universities, magazines you like to read will often have calls for content. Check out editing groups to develop a core group of peers that will help you gain more experience.
Meet and learn from writers around you. The relationships you make from doing random writing gigs will often lead you to more opportunities.