What to look out for?

Not carrying out a full handover inspection

Failing to remember that the Building Act places ultimate responsibility on clients may result in you underestimating the importance of involvement throughout the handover process. Ideally all builders should ensure their work is of the highest standard and that it complies with all applicable regulations. However, if the work is signed off at practical completion  without a thorough inspection and anything goes wrong in the future, you could be liable for the damage depending on who the main contractor was and how long it happens after building completion. Any costs incurred by you after final sign-off are not the builder’s responsibility.
Not understanding lifetime costs
You also need to be aware that the cycle of design and construction is very short compared to the whole life cycle of the building. This means that significant costs of a building are incurred after it is completed, on maintenance, repairs, utility bills, etc. Becoming a knowledgeable user, monitoring performance, and committing to constant maintenance and improvement are essential to reduce the running costs of the home and improve the life of systems and materials. ​​See ‘Lifecycle Costs​’ in the Sustainability hub for more information.
Not properly defining the end of the contract​
The contract needs to give you the ability to ensure that the builder and subcontractors finish everything to your satisfaction and in a timely manner. 

In some forms of contract you withhold a percentage of all the payments made to the contractor through the course of the contract - 10% is an accepted sum. At practical completion you would release half the money and hold the rest for the duration of the defects period. This could be 3 - 6 months after practical completion. At the end of this period all parties meet and if all outstanding​ matters have been addressed the rest of the money will be released. It is very important to define in the contract what is expected at each point. ​