Employers' budgets and priorities vary wildly. Some employers honestly don't care about the logic and grammar used in articles they purchase; they just want articles that are stuffed with keywords. These employers often hire writers from India, the Philippines and other places where people speak decent enough English and accept low wages (from a US perspective). The going rate can be one cent or less per word. US citizens are also working for this rate. It works out to a few dollars per hour and is sometimes less than minimum wage. Ick!
Other employers respect and want well-written material. In my experience, they'll pay from 5 cents to $1 per word for a web article or promotional brochure. Many major magazines pay fifty cents to $1 per word. Other magazines pay just $20 or $100 for a long article. Major variation.
I *really* wish that writers would remember this: Your work is valuable. If you write a tooth whitening article for a dentist, he or she could easily get thousands of dollars of business as a result. And if you revamp someone's resume, you could change their income for life.
In short, pay varies wildly. Don't sell yourself short! You can gain valuable practice and experience working for the "article farms," but you won't stop worrying about bills until you treat yourself as a professional and request the pay you deserve.