This is probably only a partial answer. I program, rather than make videos. But the same sort of situation can occur. I'm helpful, and early on in my career I had been asked by associates if I'd help them set up a website. I helped a couple of these people, but most of them approached me with a contract they wanted me to sign. I feel like the reason I didn't help any of these people might be useful to you.
All of them approached me with an already written contract to introduce the topic. Speaking with them about it, they did not intend to provide me any ability to adjust that contract. There was very little about the contract that I had a particular problem with. The only aspect there was that they were very clearly written from the perspective of someone who hoped to make a lot of money off of the website I was to help them make, and I was to neither get any compensation nor credit.
I personally feel if I'm helping somebody out with something not related to my job, and they want me to sign a contract, I should have some input into that contract. Even if it's the perfect contract, I'd be a lot more comfortable with it if I have an opportunity to make a change. (This doesn't mean I want one thing wrong so I can fix it, I just don't want negotiations to be completely ruled out from the start.)
If I'm going to contribute some effort that would normally be the product of a paid employee or contractor, and I'm (possibly) not getting paid a significant consideration, I should be able to decide if my name gets put on it or not. I'll admit that two of the people who approached me with a contract for my free assistance would've lucked out in this regard had they given me the option and otherwise everything seemed reasonable to me, as I'd want no credit for what they wanted to do. But other times, I'd have at least wanted my name on a Credits or Thank You page.
If somebody is going to be trying to make a business out of what I've assisted them with, I'd prefer to not have them rule out monetary reimbursement so dramatically up front. I admit that paying someone $1 at the outset of such an endeavor does not necessarily preclude any future returns, but the vast majority of times I've heard of someone offering free assistance to someone, that turning into something big for the person helped, and the person doing the helping getting reasonable compensation after the fact were instances with no contract. When there has been a contract, that contract almost always stated some provision for the possibility of such additional compensation explicitly.
This doesn't mean it would have to be written in to such an extent that it would be financially detrimental to the person being helped. It's possible it could even be written in such a way that it explicitly would only kick in at such a time when it wasn't particularly financially detrimental. (Maybe it would mean a slightly less lavish vacation, for example.)
This answer only covers a few of the things that people could potentially be at odds with, because I was only patient enough to even consider entertaining such ideas for a short while before my response to the question about helping out with the website at all was, "You know, I'm really not that kind of a programmer."
I do feel like it's probably better to have things spelled out in writing for commercial ventures, but I feel like the information exchange should be a bit more even and start earlier on in the process before springing a sheaf of legal paper on them.
