Due diligence is the boring bit that saves you from a bad decision. The list isn't long, but skipping any of it is where people get burned.

A qualified building inspector walks the house and writes up what they find. Costs $500–$900. It won't be a totally clean report on any home, but it should tell you what's cosmetic, what's a project, and what's a deal-breaker. If the report flags something big, you can renegotiate with the seller or walk away from the deal.
The council's file on the property — consents, hazards, drainage, code compliance certificates. Costs $300–$400 depending on the council. Wellington LIMs are worth reading closely: slope stability, tsunami zones and heritage overlays all show up here.
Get an insurance quote in writing before you go unconditional. Some homes (older weatherboard, homes in flood zones, unusual construction) are hard or expensive to insure — and no insurance means no lending.
Your lawyer reads the sale and purchase agreement, checks the title for easements, covenants and cross-lease weirdness, and looks at the LIM. This usually happens in parallel with the builder's report and takes 3–5 working days.
Send it through and I'll come back with a straight answer — no fee, no pressure.
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