Faith, I see your point, but when I am talking about samples, I am meaning the portfolio samples that you’re talking about.
I am a full-time writer and I still don’t have an official “portfolio,” I simply have pieces I use as writing samples when asked.
Even if writing a trial piece for a new client (I believe you are talking about this), never EVER work for free. If you give it away for free, then your work loses value (at least in the eyes of the client). You can offer a “one-time discounted rate” so that the potential client can see your work, or you can say “I’m sorry, but I am not able to do this for free. I can charge a discounted rate of $X or I can provide you with samples of my writing.” If you have samples/portfolio pieces, there is no reason or justification they can give to ask you to work for free, even to “just see if you’re a fit for us.”
Even on your very first day as a writer, never tell anyone they are your first client. Trust your skills. “Here is a sample of a piece I wrote about fashion and beauty. My rates are $xy.”
People who get something for free assume that they deserve to get more for free. They will try to negotiate down you prices and squeeze you for anything they can. YOU must value yourself and your work highly, so that others will, too.
And in my experience, it is the cheapest clients that are the most demanding and most critical — and unfortunately, the ones least likely to pay. Don’t go with the lowest bidder, market yourself as competitive.