NAH so far :) I think it’s pretty normal for students to help check over each others work, and you’re not writing the essay for them, so I don’t think it’s such a tragedy to not be paid, but I don’t think you’d be an asshole for wanting to be. Although it’s a bit unclear what you’d be charging for - would you just charge for the time you spent editing essays? You mention bouncing off ideas - would you charge every time someone chatted about the topic to you? A bit of discussion about these topics should be expected between students - asking for payment after would be a bit absurd.

If you did want to make it a kind of mini business, I would advise you first checked how plagiarism rules work at your Uni or college, as in some places editing each other’s essays may be considered cheating and taking payments for it puts you at risk.

Also, you should probably make it clear to people whose essays you often check over that you want money for it now, and stop offering them help, or at least making it clear that you want payment when you offer.

Do others ever help you with your essays? If they do, you should expect to stop receiving anything you plan to charge for, and you should be prepared for most people to just say “Nevermind, I’ll check it myself,” as there’s a huge difference between a friend offering to look over an essay and someone paying for someone else to check it. Personally, I would only do the former.

It’s not an asshole idea immediately, but I would absolutely advise thinking it over to not be an asshole about it :) good luck!