A good architect will save you money providing they have a good working relationship with the building contractor and they have a thorough knowledge of construction methods and site work. Part of their job is to reduce risks to the budget by anticipating them before they occur and to advise you accordingly.
If you commission a house design then you will want to cover off as many points as possible and the best way to start is with you "Absolute Wish List". Everyone needs to be clear what the minimum requirements are, what is up for negotiation and how much this is likely to cost. No doubt you are looking for some clever design ideas and the wow factor otherwise why bother with the additional cost?
The initial stages should just be on paper as your designers starts to sketch out possible combinations of concepts and this is definitely an interactive and exciting process. Get involved as much as possible and send your designers lots of ideas using platforms like Pinterest.
Planning can be a breeze or a major headache and it could be in your interest to engage a planning consultant. They know the intricacies of the law and what you are most likely allowed. There are always exceptions to the rule but if your consultant thinks it's unlikely that you will get permission, they are normally right!
Once consent is obtained, the house must be buildable to the budget you have allocated. It is not the contractors job to rectify bad design and this is where the relationship between the two will make your life so much easier. Before you start your build, have an onsite meeting and ascertain if there is any tension or resistance. If so, find someone else to work with.
About 80% of an architect's time is spent calculating construction details and specifying materials. All of the decisions have a cost implication but the one most overlooked is time. Your builder must work to the time schedule set out by the architect. A contractor is usually paid at regular intervals for completed work up to that point.
You could also set up a contract so that you don't have to pay the builder for work until the architect has inspected it, assessed its value and issued a certificate stating how much is due. However, even the best laid plans can go off track so flexibility is key as there may be additional unforeseen costs.