Mum or Dad are growing old, a bit weaker, and need someone to keep an eye out on them. But they want to maintain their independence, to have their own kitchen and bathroom. No idea how long, perhaps a year perhaps a decade. Their kids want to help.
The kids own their own home. It has room to park a mobile trailer home in the back yard and plug the utilities into their house. They prefer to lease it on annual leases so the lessor can take it away when no longer needed. From a council perspective, the effect on public utilities is no different than Mum sleeping in the guest bedroom, but from a social perspective, it is world apart. They have autonomy. The rent is affordable (say $250/week) and there are no complications like building a granny flat that involves builders, plans, chaos and noise during construction, and, once the need is over, the kids are stuck with an empty building to tear down or pay rates on.
But, if the kids go to the council just to make sure there are no issues, it suddenly becomes a major issue. The council tells them it is a building. It will require a resource consent and a building consent. Typical cost for those who comply is $25,000, the equivalent of two-years rent. The council is wrong. It’s not a structure under the RMA, and not a building under the Building Act, but opposing the council is a costly, miserable exercise. The kids give up. Nan goes to a retirement home.