Telling Maya so vaguely was pretty lame.
Since the mc had a better relationship with Maya than she had with Sage or Quinn, he could have easily approached it.
mc: "Look, this is gonna sound crazy, but I think Quinn in running a prostitution ring with the girls from the HOTs, I'm not sure of the details, just be fucking careful."
Maya could have responded however she liked
Maya: "I doubt it..."; or
Maya: "Woah, thanks for warning me!"
Either way, the mc would have done his duty.
Ultimately it wouldn't have made a difference. Unless Maya realised then and there it was associated with the free tuition, nothing would have changed.
Telling Sage, who the MC only knew for a few weeks (even if they were fucking) while she's known Quinn for a couple of years, could have gone pear shaped.
mc: "Hey Sage, before you suck my dick, I just wanted to mention, are you aware that Quinn is running some kind of prostitution ring with your girls?"
Sage tends to react aggressively to some things, this might have been one of them.
Sage: "Are you fucking kidding me? I know you and Quinn have had your differences, but this is bullshit, I can't believe you'd make up shit like this. You know what? I'm not sucking your dick now!".
mc: "Fuck me!"
Sage: "Not happening"
mc: "..."
Sage may have taken it more seriously.
Sage: "Are you serious? How do you know?"
mc: "Quinn offered me some weird bullshit restaurant membership, 'Hot and Spicy', 'Japanese', I'm pretty sure it's a euphemism for the girls' nationality".
Sage: "Fuck, I hope you're wrong, I'm gonna have to speak with Quinn..."
Sage then confronts Quinn.
Sage: "So what's this shit I hear about you using our girls as whores?".
Quinn: "That fucking pervert!"
And then you just made enemies with probably the most conniving, vindictive cunt on campus (after Sally).
You know what, I think mc will just keep his head down...