Hi macfod,
Welcome to the forum!

Seems like your best option is the Long Term Business Visa. If you plan on taking over an existing business, this can be an easier process.

Requirements are:

You MUST have had business experience, either running your own, or at a senior management position.

You MUST have funds to support yourselves for up to 2 years (although NZIS do not specify the amount, $30,000 a year is a good basis). These funds must not include the costs of starting up your business, they must be seperate after all business expenses have been met.

If you have been involved in fraudulent activity, or have run a business that went bust then you will be declined.

LTBV is a difficult route to go by, but its the only way if you want to jump straight in to running a business.

I'm sure you have lots of questions, so dont be shy on posting them!