I think Wendy had the best value of any Air BnB we used in New Zealand. If you're looking for a great place to stay in Christchurch I would strongly recommend choosing this one. You might think it's a bit far outside of the city center, but unlike most Air BnB rooms at this price, you will get a private bathroom/shower, a big room with a great bed, and super friendly hosts who will most likely give you a free ride or two during your stay. They have also prepared a binder/folder in the room with tons of useful information for visitors.
Of course, many people will stay here because it's close to the airport. Just FYI, our Uber took 10-15 minutes to arrive after we ordered it at about 5:15 AM. It cost $21 NZD and took about 8 minutes to get to the airport.