Ask HN: Partnership agreement for new idea?

Hi -

I intend on working on developing an idea into a product with a partner. We don't want to incorporate yet, we want to develop our idea first.

I am wondering what type of agreement people put in place when they don't want to form a business yet, but want to have some sort of governing document for their partnership.

I intend to involve an attorney to develop formal paperwork, but I like to be informed before I do so.

Thanks for your insights.