Brothels in fantasy

There are brothels in the Jewels of the Blood fantasy series (not YA though).

In the Ranger’s Apprentice series (MG/YA), an older Ranger tells a young knight (with total seriousness), when asked why some of the girls are wearing such short skirts, that they are messengers and need short skirts to "run fast". The knight agrees that, yes, it would be easier and adds, its also much nicer to look at. Its clear, the way the scene is done, to an older reader, the girls were prostitutes.

I don't have a problem with it, as long as it fits the story.

Well, that depends on which Earthlike culture/society (if any) you're trying to imitate in your work. Prostitution has been pervasive in human history, but it didn't/doesn't always involve brothels.

...are too few and far between for any real adventurer's liking.

Brothels have their place. I think it depends on how you want to portray the world. And like Entropy Perk cited, there are ways to disguise it for a younger audience and that maybe better because then people go, "Ohhh I get it." Though I'm not sure if you need to disguise it for YA.

At any rate, their in my works. One WIP takes place in a Brothel.

No brothels in my fantasy story (which from what I've read around here could easily be categorized as YA), but in one scene the protagonist goes to town with a friend and spots some Victorian-era prostitutes hanging about in the Fur Company. She can tell from the way they're dressed and the way they giggle at her what they are, and is of course mortified that the place she knows has changed so much. When she sees them I just say that she can tell what they are; later on in the story she makes use of the word "prostitutes" or "hookers," I can't remember which, maybe both. (She's from the modern day herself.) By extension, I guess this means there could be a brothel somewhere in my story, but it's never referred to.

In a sequel, when she mentions the word "hookers" or "prostitutes" to an eleven-year-old girl who then asks what those are, she says, "Have your parents tell you when you're older." The way the girl reacts--saying, "Oh"--indicates that she at least has a vague understanding of what that means.

That's all there is to that particular matter--the reader is informed that this place does have prostitutes--there's no sex or anything. Based on what I've read around here this is pretty tame for some YA, so just having brothels in a YA story seems okay to me as long as it's not going to get all graphic!

I should note that the mention of my fantasy location having prostitutes is tame itself compared to some of the OTHER stuff in my story!

How you describe it, seems fine to me.