For anyone who is planning to do a cycling trip in New Zealand, no matter you are starting in Auckland or Christchurch, you can easily buy a second hand bike with a pretty low price, and they are in good quality. I have done some research before, these 2 shops have branches in both North and South Island, but their price are not that low, around 400-600 NZD to have one with all the necessities (front and back racks, bottle cage, pannier bags…):
http://www.aroundagaincycles.co.nz/
http://www.bicyclerentals.co.nz/biking/used-bikes-for-sale/

But if you are not that fussy, try Trade Me:
http://trademe.co.nz

It is the eBay in NZ, that you can bit your desired price or Buy Now. I got a bike from Trade Me which cost only $110, plus $15 changing the handle bar, $12 on water bottles and $50 buying a pair of second hand pannier bags. So in total I only spent $187 on my bike. Quite awesome, hopefully I can sell it in similar price!

And then I met some other travelers who plan to tour around NZ in a campervan, it is like a 8-people van which convert into a moving house, with mattress, cooking equipment, light and all sorts of things you need to travel around. The price is something around $3000-4000 depend on the model and season, try to buy one in low season (winter) and sell it in high season (summer) and you might make a profit!

Another way to wander around NZ is hitchhiking which is VERY COMMON here, unlike Australia, the Kiwi don’t have too many suspicion on travelers, and most of them are happy to do a charity a day to help you!

Will start my bike tour tomorrow…exciting!!