Screenwriting : The Business of Co-writing by Benjamin Grund

Greetings Stage 32'ers. As the title suggests, this is a question on the business of co-writing a screenplay with a partner. If approached by a professional I've met but don't know terribly well, what questions should I be asking? Is there an etiquette or a protocol involved in discussing how credit and payment will be handled? Many thanks in advanced everyone. Cheers to the next draft.