I hope it's not a "freelance journalist specialising in travel" because taking a freebie or a discount, unless that freebie or discount is revealed very prominently within the story, is considered unethical behavior within the profession of journalism.

Yes, it happens, but that doesn't mean it's correct.

Every time I've traveled on a story either the publication who assigned me the story pays my way (if I'm freelancing something and don't have a buyer yet I pay for it myself and either get my costs recouped by the article's purchaser or I take a business expense tax deduction) or I say in the first two or three paragraphs who subsidized the trip.