Will a New Plymouth business come to Hawera?
For a decent-sized job, usually. For an hour's work it is an hour each way, so expect either a travel charge or a suggestion to use somebody closer — both of which the quote will say plainly.
Who is allowed to give immigration advice?
In New Zealand, a licensed immigration adviser or an exempt person such as a lawyer. Licences are searchable on the Immigration Advisers Authority register, and it is entirely reasonable to check before engaging anyone.
How are fees charged?
Commonly a fixed fee per application, sometimes staged, and always separate from Immigration New Zealand's own fees and levies. Ask for both numbers so you know the total.
Can they guarantee a visa?
No, and anyone who does is telling you something they cannot know. What a good adviser offers is an honest read on your chances and a properly prepared application.
What if my application was declined?
There are reconsideration and appeal routes with strict time limits, which is why this is the situation where advice earliest is worth most. Say it has been declined and when, in your request.