Re: Seeking advice on getting paid

IANAL but the email is still a documented communication and the first payment an acknowledgment to the agreement.

Without exact wording you used it's hard to make exact suggestions. "Upon Delivery" can mean different things to different people.

This sounds like a small job dealing with an individual or small organization. IMHO the payment crosses your palms as the DVD crosses theirs. Offer to pick up the check (which still isn't secure because it can be canceled) when you deliver the DVD. I'd say explain that "Upon" does not mean after. Bigger businesses can be slow but there's no reason a small organization shouldn't have the money ready for you for an approved project. If they want an "approval" copy first so they feel comfortable with the quality of the work, I'd consider posting a Window Burn In (or other watermark) dub online (Vimeo with password protection and viewer download blocked might work).

Better wording might be "payment to be received at time of delivery." BTW that's why contracts drafted by lawyers are so awkward for laypeople to read. The language has very specific meaning and intent.