I like Eric's approach, that is generally how I operate. I will of course allow for 30 day invoices with established companies or people I have worked for in the past. I am, however, in a bad situation like this myself.
I am owed a good deal of money by a production company that promised to pay in mid October. They are telling me about various ways they are trying to get the money but it's just not happening. Basically they operated outside their means as Philip described. I'm not sure what to do about it. It was for a cable show with producers I have worked for in the past (under a different company) so I trusted them. Would anyone recommend taking legal action in situations like this? It seems to me that if they don't have the money, they never will, so I'll never recover what I am owed.