The Verdict: Need More Info
Every scheme starts at 18, so you can apply once you turn 18. Note your country's opening date for that year, because capped schemes close when full.
Most schemes run to 30, and nine to 35. Most give twelve months, with Canada at 23 and the United Kingdom at 36.
Until then, a student visa or a visitor visa are the ways to spend time in New Zealand. Under-18s travelling without a parent or guardian need care and accommodation arrangements that Immigration New Zealand will check.