I'm picking you are not a landlord as you are not coming from a position of knowledge. Or if you are, not one of those who lodged 90% of applications against tenants in the Tenancy Tribunal last year. Most for rent arrears and/or damage some of which will never be recovered and some drip fed over years if the landlord is lucky. Not to mention vacancy time while repairs are done, and the significant hassle factor. Landlords have to give 90 days notice (usually) for a periodic tenant at the moment, tenants 21 days which works in the tenant's favour.
IRD has said publicly that residential rental owners are not advantaged for tax compared to commercial / far / business owners. And in fact they are disadvantaged since building depreciation was removed for residential rentals.