Ask HN: I'm a student with a Mac App; how do I sell it?

Hi HN! I'm looking for a bit of advice as I'm a complete beginner to selling software. I've created a Mac App which I can't distribute in the Mac App store (It interfaces with some Apple software, and I'm certain Apple would not approve it). I'm looking at creating a website for the app, and signing up with Braintree to process payments, but the whole process is rather daunting, and I'm afraid of legal aspects I might not be considering (I'm selling a product; I don't want to make any legal mistakes that could get me in trouble).

Can anybody offer me any advice on how I can monetize this app as a student, without having to pay big fees in business formation/ etc.?

I hope this community is right to be asking this sort of question in!

Thanks in advance!

- Chris