There is a huge lack of 2 bedroom homes in New Zealand. Even 3 bedroom homes are in short supply, however getting the right 2 bedroom property in key areas will give you a great rent yield versus purchase price.
Smaller homes in well selected areas can be a great way to get your foot in a hugely desirable housing sector.
Again this lends itself to multi dwelling properties as well by having a duplex style property. However this is probably an area where there is more demand for rentals than any other housing style in New Zealand.
Having a good property manager to vet your tenants is the key to managing smaller homes. Most people are good tenants but a attentive property manager will ensure you get the tenants you desire.