cpa, I am not a cpa, but I beg to differ...
From an accounting standpoint you either have revenues or you don't, period
I recently signed a contract with a customer that had a 15% downpayment component. We received 15% of the total value of the conract at signing (actually, when the performance bond was delivered)
The money showed up in the bank and certainly aids the cashflow, but is not recognized as revenues until work is performed
"Absence of evidence is not evidence of absence. - Carl Sagan