A social enterprise is a business which also has a social purpose which becomes a big part of your marketing strategy. How you start a social enterprise is the same decision process as a business – https://www.business.govt.nz/starting-a-business/
The only other consideration is whether your business would also:
Benefit from becoming a charity, and
Qualify to become charity
A social enterprise can have profit objectives, provide you with an income and still deliver social outcomes.
A charity that is a social enterprise can have profit objectives, deliver social outcomes (your charitable purpose), and provide you with a market value salary but all additional profits return to your charitable purpose. The biggest benefit of charitable status is exemption from income tax. On windup of the business, all surpluses would also go to your charitable purpose. There are additional ongoing compliance costs of setting up as a charity including setting up an independent governance board, the obligation to file an Annual Return including financial statements and depending on your turnover having an annual review or audit.
If you decide you want to create a charity, Charities Services outlines the criteria here – https://www.charities.govt.nz/ready-to-register/need-to-know-to-register/charitable-purpose/ They also provide other information on getting started – https://www.charities.govt.nz/ready-to-register/starting-a-new-charity/
While becoming a charity has its attractions, when in start-up you may want to consider starting as a business, working out how to make your social enterprise model work, and if it’s sustainable at a later date restructuring and applying for charitable status.
For a more extensive chat you may want to make contact with https://thegoodcollective.org.nz/ – “Think like a Business, ImpACT like a Charity”