Child prostitution was basically legal in NZ up until 2013. Now it’s pretty much just frowned upon. Check out this article from 2010.
"Her parents knew exactly what she was doing."
"They're just happy a few dollars come in each week, because a lot of them will spread the money to family”
https://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10651367&pnum=2
If you are a brothel operator, or a client, you can be fined or imprisoned if you hire a sex worker who is under 18. It is also illegal to receive money from a sex worker under the age of 18. It is not illegal to be a sex worker if you are younger than 18. However, if you hire a sex worker under 18 to work in your brothel, or if you are a client who hires a sex worker under 18 to provide you with sexual services, you are breaking the law.
https://web.archive.org/web/20071229172420/http://www.nzpc.org.nz/page.php?page_name=Law