>>edit: i guess i wasnt clear enough. Im not selling a computer, a service. I should just get his address, that way if he doesnt pay, I'll kill him ::evil laugh::<<
it all depends on whom is "buying" your service.
most companies, including DoD (the company i work for) WILL NOT pay for services until they are completed and reviewed for completeness and satisfaction - then and only then is payment made.
if an individual party is "buying" your service, do like rod or ober suggested, or you can even ask for half up front, and the reaminder upon completion.
the money situation is pretty much figured out, its only the profit share im worried about. I dont really want to go on his word that he's going to give me a certain percent of the profits that we had decided on, he could just say "F U MAN" and not give me any more money.
that's what quotes are for.
ideally, he should say - you need to do blah to blah's blah. then you say that'll run so much. he would need to agree or negotiate with you. do it via email or make him sign on (at least) the final qutoe and go from there.
you may also ask for a SOW (Statement of Work) that basically spells out everything you are expected to do, including what you are expected not to do. this is sent/given to you and you can then accept it or return it with suggestions for changes and go from there.
this is only valid if the person you will be working with is going to pay you on "as needed" basis.
profit sharing - that isnt handled in any part of contracting that i do.
Don't sell junk and you won't have to worry about it.
Note: Since I'm pretty sure no one here's actually a lawyer, none of this should be considered sound legal advice, so take it all with a grain of salt.