A guy walks in to a Starbucks...

The magic words for me are, "the guy is willing to pay in advance" -- hoot!

Agree upon and make clear to him exactly what he's paying for. A first draft? One rewrite? Time limit -- how quickly can you write the draft? A couple of weeks? A month?

If this were me -- I repeat, if, me -- I'd hit him for 500 bucks and start typing. Not an unreasonable sum based on the number of hours I'd expect to be working on it. You know yourself best, do your own arithmetic.

-Derek
Warning, the above message may contain my personal opinions, which are not necessarily balanced, never mind correct.

Call me uptight, but stuff like this can get tricky. If I were you, I'd approach it like a contract negoation and put everything on paper BEFORE I agreed to anything. That way, if he pays you $500 to write a script and it doesn't sell, then he can't come back and sue you for the money back or for any guarantee he feels you implied by taking his money.

You need

EVERYTHING written down and signed, even notarized.

Start making a list of all kinds of things to discuss and negotiate.
Be honest with your guy. Send him to some website maybe so you and he are talking the same language.

Your basic agreement will be that he is the idea man and you are the screenwriter. That means you work with him to help him understand how and why some things work and others don't.

Your meeting with him over coffee is mainly to see if he will listen to you and help you get a sense of each other. Brainstorm some questions for him, interview him about his goals for the story, what he wants, what his vision his, what his hopes are, what he will or won't accept.

Then tell him to write up his issues, things he expects from you, his terms.

Maybe you should work on a pay as you go basis. Fifty bucks for the outline, 100 for the first 10/20 pages, 500 for a full on first draft, so forth.

Meet again in a few days/weeks and see where you are at.

Does his idea appeal to you OR do you just see dollar signs?

I admit, money is always great BUT it is really, really, REALLY hard to slug through a project you can't get into, that doesn't have some value to you personally.

This may be a good chance for you, and if you have some bills to pay, well, then go for it.

Script

I'd write it, but not for five hundred lousy bucks. That isn't even slave wages.
This guy deserves a final, polished draft. You can't do that in a couple of weeks. Give him less than this and you're just stealing his money. I might do it for five thousand dollars, but not for a penny less.

Scripter has some really good points. I wouldn't do anything until all standards are perfectly clear. The first thing I would do is make him understand that even if he is putting his money into this the script there is a very good chance it may not sell, therefore he will not be getting his money back. Also since you will be the one doing all the work, and him just the idea man, I would atleast ask for 75% of the profits.

Steph