At the minute i prefer the build option as you know you are getting a house that is up to current spec, but there are some bargains to be had if we are willing to renovate.
Old houses built 25+ years ago generally have no major problems at all as if there were any, they would of showed up by now. It's also important to know that old houses with wood floor joist on pile construction do not have the insulation as modern inslab polystyrene insulated concrete floor slabs of today's homes. Prior to the 80s, virtually all houses in NZ were constructed with wood over concrete pile construction and a general upgrade in insulation is by installing polystyrene between the wood floor joists. This still does not address the cold air that is vented under the crawl space. In many issues, and i'm speaking from an energy efficiency point of view, it's not cost effective to turn an old house into a standard of a new house. Many of the old timber framed houses purposely had holes drilled in the bottom and top plates of the wood framing for the purpose of ventilation - so you would have to address this before installing insulation in the wall cavities.
The risky houses to watch out for were those built recently say post 1990 when there was a lot of changes to the building act. One being the ban of treated timber framing and the introduction of EIFS (external insulated finishing system a la monolithic polystyrene cladding) for the house exterior. The use of untreated timber framing did not contribute to the 'leaky house syndrome" in NZ but rather, it accelerated the rate of how fast a house will go rotten. A
must read below for any potential home buyer:
http://dontbuyaleaker.weebly.com/
It is even more important to note that a building inspector does not offer guaranteed protection in buying a bad house. Majority of these inspectors go by visual and no home seller would be willing to allow any inspector to poke holes in their walls to get a more accurate reading if the walls contained moisture or not (or inspectors having the required tools for inspection). Furthermore, NZ building inspectors are not required to go through any formal training or certification scheme (which is a shame considering how expensive buying a house can be). In Canada the province of Ontario is in the process of implementing a certification scheme for such building inspectors shown here.
http://www.youtube.com/watch?v=TxM90...ature=youtu.be