The document discusses when billing is due from clients. It suggests that billing is typically due either upon receipt of the invoice, within 5-14 days of receipt, or for hourly work, on the same day each month. While getting paid 100% up front is ideal, negotiating 50% up front is also acceptable. Invoicing after completing all work (billing in arrears) should be avoided as it increases the risk of clients not paying in full or at all.