When young writers start out, you almost always start by writing for a byline. No cash, no contracts (as we talked about last week), only the pleasure of saying you got published in Examine Your Zipper or Orlando Bloom Quarterly. I've been freelancing for four years now, and only write for free in several situations.
Exploring a New Market. Travel is something I'm interested in writing about, so I'm hunting for travel zines or travel columns regardless of whether they pay. Once I've earned my stripes, I'll go after the heavy-hitting (and big buck-giving) travel zines (Geez, what's with the participles?).
Establishing a Reputation. Columns or guest positions are fantastic because now you can say, "I'm a columnist for Angelina Jolie Live Always and Everywhere." If you're offered a column position, take it. Your reputation will benefit if you do a good job (Hint: always keep track of your deadlines!)
Giving Back. Sometimes I write for free when I like the magazine editor and she's helped me out before. Write if you believe in a cause and want to support it. If there's a "giving" aspect, think about writing. Your art is not meant for pure profit.
The Prestige of the Prestige. If a big name approaches you about doing a piece for no cash, think about the name. In the bio part of your query letters, you don't put how much you were paid for an article, but you do note what the name of the magazine was.