Netsuite allows creating Non Inventory Items for Resale even if the expense and income accounts are blank. There will be a pop-up message that says: “You must specify accounts for this item to be available on transactions. You may want to leave them blank if this is to be a parent item or a component of a kit or assembly.”
However, if an income account is added and the expense account is blank, I receive the same message: “You must specify expense and income accounts for this item.”
This is because, by design, these item records are used to track something you buy and then sell for a profit, but do not stock.
Since this is allowed to be bought from a vendor, an expense account is needed for users to track the expenses made on buying this item/service. Without this, the item/service will not appear on Purchase Order transactions since there is no account specified to charge the purchase..
So ultimately if you decide to enter the accounts then you may need to fill in both of these accounts from the system to save the record.