Questions to answer first;-Based on property locations, what demographic are you targeting for tenants?..

The only demographic that has a better chance of being more qualified are the young 20-somethings, maybe they are single or recently married, and not ready to buy yet.

demographics change lots of things can happen in that industry just like any industry.. and for sure burnt out landlords create opportunity for new blood coming in.  

The beltline goes through a wide range of neighborhoods(over 20) with a wide range of price points and demographics.

When targeting use the demographics and behaviors of your target audience (i.e. likely to move, divorced, homeowner, etc...).

I use very specific language to a specific type of property to a specific demographic.  

Demographically speaking the area has a low purchase price to higher rent ratio.

However the working population is moving away so as the demographic ages and there are fewer children these areas can see a decline in demand and values.Stick to the big 3 is your best bet.If you want some more local town information there is a very good NZ forum called propertytalk.com.  

This is where BP will be invaluable as you will be able to network and find investors local to the areas that interest you - local knowledge is essential to ensure you do not purchase property in the wrong area; that you understand the local climate, demographics, economy as they all factor into your investment.

Though I think properties with ADU on them will see an increase in appreciation I do not think it will have much of an impact on the local housing market because:1) Not every home has space for an ADU2) Not every home with the space wants an ADU3) Not every owner who wants an ADU can afford to build oneIf ADU took off it would only help a small demographic of the housing market (i.e. those with smaller households [1 to 3 people] ).