FTB is not earnings.

If you are sure you will not earn any money (even from shares etc), put your income as zero Jo.

Whatever you do Kell, do put in the income regardless of how it will affect your ftb payments. The tax dept cross checks and you will get stuck with a debt. You will get more FTB part B when your income is lowered.
FTB part B goes on the estimate of the lower income earner. If you are single you don't have to worry about it at all, you get both.
SO - yes your FTB part B will be slightly higher if your income is zero, on 07/08 rather than $8000 or so, but you must be sure you won't have an income for the entire year.

You can only incur debt if you choose to get ftb fortnightly.

Keep the questions coming - I have a direct line to c'link if the ?? get really hairy.