Remember your first $ is taxed. First work out what your after tax take is. Visit the IRD site for tax rates. For rents visit
www.trademe.co.nz Rentals vary quite dramatically in quality and price but my friends rented a 2 bed in Island Bay (nice but not over the top suburb) for $420/week. We pay about $250/month electricity. Some can pay a lot more; somewhat dependent on aspect - don't get a rental with southern aspect! If your kid is older you may want to look for rentals in the central Wellington zones for some of the best schools in the country. Food can be quite expensive until you work out the hacks. Bear that in mind. $100k is reasonably good for Welly but you prob wont be saving too much.