How to approach contract agreement
 

I've just started working with someone who is beginning an artistic project, documenting and following around the artist. For free, as one part of building my demo over the next month or so. This project is gaining support from sponsors and could conceivably grow into something much bigger, possibly into a concept for an organization that would raise money for causes from the artist's work. It seems to be growing quickly.
I am considering proposing a video partnership with different, documentary-type work that I would do, that would complement and significantly expand the scope of the project. Or maybe, rather than as a partnership, I just do the work in in the same capacity I do now, as sort of the resident videographer. Not sure yet how that would work. Either way it would come under the umbrella of the project.
If this ends up being a possibility, I'd prefer the partnership route. At any rate, I definitely want to own my work. I figure if this is going to go past the very basic stuff I'm doing now, (following the artist around for a few weeks), it's best to approach it with a written agreement.
What should I know or keep in mind?
If it would work out that my part of it was saleable, i.e. DVDs, later on, how would I approach that now?
I also don't want to be intimidating and want to approach it lightly - this has literally just started in the past week. I do believe though that agreements are best done in writing just so everyone is on the same page.
Thanks in advance for your suggestions.

Kell, first you decision to get a written agreement in place early on is a very good one.

Second, since the artist isn't paying you for your work then the contract should be clear that whatever you create belongs to you and you can do with it what you wish. If this seems unfair turn the situation around. Is the artist you're documenting going to share revenue with you for the works he or she creates? Probably not. It's a mutually beneficial relationship so you should benefit from your creation just as the artist benefits from theirs.

Thanks Rick.
Here's a thought. I might consider for a time doing the work for free for a short time even if things got more extensive, since it's a project worth being involved in. However, if it became funded and the ability was there to pay me, I'd like to do that. The scenario I was envisioning for a contract situation would be along the lines of me being full time or maybe a little less, or a situation that would include travel. If it just stays where it is now to build a demo, I'd want to own my work, but the situation would remain much more simple than if it headed down the road of employment, partnership, or something that might involve item sales.

With these kind of projects where often there is little real 'money' likely to be generated by either party, I usually build in a section where, if I make money from it, I pay them an agreed percentage of my profit, and in return, if they sell some of my product, we do it that way around. Despite pieces of paper, there's obviously trust involved here - so I rarely offer this kind of split to new clients, but repeat customers usually get the offer. I'm quite happy putting my time into these projects when it's really spare. I'd rather do something in the quiet times - even if actual profit seems a little distant.

That's a great idea.
Actually I think this might have potential to generate real money - in terms of sponsor backing and sales it could potentially get very large in the future. But it would not be for profit -it would be for charitable purposes.