I've been writing fan fiction for several years. It's been a great platform to build my writing skills, and I feel ready to publish soon. The website I've been posting my fan fiction on is in fact a fan-site dedicated to a story-rich board game (so it's not a writing site, that's only a small sub-forum).
For the past several years, another user on that website has been proofreading my fan fictions for me. He gets first look at them, and in addition to correcting grammar and typos, he also offers me his opinions and insights on the story, and what I could improve, what he thought was great, etc.
I would very much like to keep this person as a beta reader for when I start writing and publishing novels. I value the criticism and ideas he gives me, and I would like to have him on board throughout my writing career.
This brings me to the question: is there any formal/official/legal documentation or anything I need for him to be my beta reader? Or is he on the same level as a friend I'd ask to check things over before I give the manuscript to the publisher? As a side note, is there any sort of documentation I might want, even if I don't need it?
Note: This person is not trying to scam me out of my writing. While I have never met him in person, I highly doubt he's out to steal my writing or anything. Firstly, he's there for the board game, just like we all are. Second, he offered free advice, and I was the one who asked him to start proofreading. And finally, he's been doing so for many years. If he is running some form of wild scam, he's the most patient scammer I've ever seen.