Disclaimer. I have not had this situation so my questions are to provoke thought.

Is a Spec House Inventory?

Is there an exception for this situation, that avoids the IRS rule saying you can't use the installment method for Inventory?

Would reporting all of the sale in the current year push him over the SS limit for self employment tax purposes, and would that savings make up for the difference of reporting all of the sale in the current year even if you can find positive answers for the first 2 questions?

Hope these give you something to research and consider.