"I would like you to paint this wall for me, and if I like it, I will pay for it when it's finished."
"I hear you are great at cutting hair. I'll need this haircut for free to make sure I like you work, then I'll sign a contract to get all of my paid haircuts for the next 12 months from you."
However, that doesn't stop people from asking.
A potential client sent me a request that I write for a job they had placed on UpWork a few days before. I declined it, being busy with other projects and most likely unable to complete the work in his given timeline. He wrote me a note, asking why I had declined the work, stating he thought mine was the "best writing I've come across on Upwork and I'd love to work with you in some capacity."
The client sent me a request to do a 600 word essay as a sample. I sent him a bill. Almost immediately I was returned with a letter filled with shock. $35 for 600 words was too high. I explained my cost per word and that $35 was the minimum charge for work.
"This isn't a job as such, although I appreciate you may normally request payment for samples. I am happy to just go by your profile portfolio though if you'd prefer."
If you were okay with my portfolio samples to begin with, why did you ask for free work in the first place?
There is no guarantee that coffee you just bought will be delicious and worth the $6 you paid for it. There is no guarantee that the apartment you rented will be worth the $1000 a month you are throwing down to live there (plus move-in fees!). There is also no guarantee that you will love my writing and we will work well together. It is the chance you take, purchasing a product. Through the right channels, you can most likely get some of your money back from a product, but not for completed, creative works. You are all in, and you are not guaranteed happiness at the end. Only completed work, a strong work ethic, near-perfect grammar, spell checked, written to the best of my ability, and within your specifications. Clients as for, and freelancers giving, free work is diluting the trade for everyone involved.
When you work for free, even as a beginner, unless you are donating your time to a charity or project you believe in, you are cheapening your work. Why would anyone ever pay a content writer if they can get new, struggling ones to do it for free? There will always be someone willing to work cheaper or faster or harder than you, so you must distinguish yourself in a different manner.
Working for free will never, ever do that for you.