Writing careers don’t always start by getting a degree in journalism or English, either (though a related degree certainly helps). Lots of writers find success by falling in love with writing later in life, choosing to freelance and slowly building up expertise and a portfolio before finally applying for a full-time job as a bonafide writer or journalist.
One thing is for sure, whether by credentials or previously published work, you must be able to demonstrate your writing skills to land a job.