I'm pretty sure "no paperwork" is bad advice. You probably won't have any problems, but if you do, they could be big ones. I've definitely heard of badly-defined rights sinking projects. It's not always because of malice, or greed, either. Sometimes it can just be a failure of communication.
In fact, just recently, I was reading about
Dwimmermount, a Kickstarted tabletop RPG supplement. The situation looks kind of complicated, and I may be misunderstanding, but apparently Autarch, the company running the Kickstarter, was paying a writer to create the supplement. But the writer currently owns the rights to it, and not them. He's facing serious family problems (apparently his father is extremely ill), and hasn't been working on the project, or contacting the company. But they're unable to fulfill the Kickstarter rewards, because technically, he owns the IP. They would be infringing on copyright if they did so without his permission.
I don't know what sort of paperwork you should put together to avoid situations like that. I would be afraid of misleading you if I gave you a wrong answer, based on my incomplete knowledge. But I do know that not signing anything, while it might work out, opens you up to huge potential problems.
I have heard of
New Media Rights, which has legal guides for "Internet users and creators". I've seen a few of their videos related to game development, and they seemed pretty good, but that's the extent of my experience with the site. I'm not sure if they'll have what you'll need, but it's worth looking.