There is no way on earth the cost of living is higher in NZ.
Even Australian beer is cheaper in NZ!
If you haven't been there long enough to qualify for the student allowance you can borrow $160 a week on top of your student loan. Its not a lot, but means you can work less and focus a bit more on studying.
18 months is if you take your time. It took me 12 months from 0hrs to CPL, MEIR, and instructor rating.
Interest free while in NZ, and if you move overseas you can freeze payments for 3 years, after which the cap on the maximum they can make you pay is $1500 every 6 months. With interest though, that would mean going backwards on repayments and never paying it off.