Anyone who does ANY kind of work needs a work visa, and this includes work for which you get any kind of recompense, e.g. board and lodging, not just money payment. This requirement has even been stretched to include a visiting grandfather, staying with his family, babysitting his own grandchildren. So you'll see that a high priority in your planning must be to sort out the basis on which you would be in NZ, and arrange a suitable visa.
If you're involved with church work, you may be eligible for this specialist work visa.
http://www.immigration.govt.nz/migra...ousWorkers.htm
Anyone who does ANY kind of work needs a work visa, and this includes work for which you get any kind of recompense, e.g. board and lodging, not just money payment.