Yes the number one rule for creatives is never deliver work without payment. I have stuck to this rule throughout my 26 years in business. Of course there are exceptions to that rule.There are customers I have a long standing relationship with, or corporate clients that are net 30. That being said, the times when I did trust customers to pay after delivery I found myself chasing money for quite some time. Who needs that. Also, sometimes it's hard for us business owners to act as our own accounts receivable dept, finding it difficult to "get tough" with the client, so I say don't. Your mantra should be, and your customers need to understand..."Payment is expected upon completion of work".