I can't really form my own opinions from such broad simple concepts but a few pointers:
A small handful of people will complain, incessantly and in a nasty tone, about "NTR" if the male MC is not the mega pimplord with sole exclusive access to every female hole in the game. Be prepared to ignore/block them.
Since the pitch does not seem to explicitly require it and you don't specify graphics some people might appreciate the option of a female player character instead. Male PCs are preferred by the majority however.
Brothels actually have been explored quite a bit, but only in specific genres. Mostly "corruption" games where a female PC whores herself out, and "trainer" games where you are the manager/pimp/slave owner. Both usually involve documented improvements in sexual skills/performance.
Since brothels are a very impersonal setting you need something beyond the basic idea to carry the game. I haven't seen any but a Visual Novel based on your idea could pay off with good writing as readers get attached to the characters. As a sex game you could make highly interactice action-oriented scenes but then the brothel aspect mostly becomes a background framework/excuse. In between you'd probably need good art, animation, a genuinely fun core gameplay loop or appeal to a specific niche fetish to stand out.
So mostly just give more information on what you have in mind, and search the Games forum for entries with "brothel" in the title.
Yeah, I'm aware of the Anti-NTR crowd.
The MC needs to get a job, as he is being pressured by his mother.
He can't find any, due to the difficulty in the job market, but an opportunity arises for him to work in a shady bar and he accepts.
In the course of the story, he discovers that it is a brothel disguised as a bar, and so he will start interacting with the girls at the behest of the brothel/bar owner.
The focus would be on the MC trying on new girls who want to join the team and teaching them how to get laid, being the male counterpart in sex.
Sometimes another girl from the brothel might join you to teach the newcomer.
There are many ideas I can develop from that beginning.
The MC will be the central point of the game, so I won't show the scenes between the girls and the customers, even though it's implied that this will happen.
I believe that this kind of story isn't even considered NTR, as there won't be any emotional ties between the characters, it's kind of the MC's profession.
I also don't intend to include mind control, or corruption, or anything like that.
I like the idea of it as a resource management game - I'm imagining a football manager game but with hookers. I'd play that. If you want to avoid the three letters of doom, probably just only show sex scenes with the MC.
Edit: Or lesbian sex scenes. Yeah, just put in lots of those ^^
Good ideas, specially the lesbian scenes!
There will be context to include some of them, so I believe that will be part of the package.
As I said above, the MC will kind of be a helper to the brothel owner, so it will be something geared towards a management game indeed.
But that will only be in the story itself, as the gameplay I intends to keep it in good old Visual Novel style.