After a site analysis and a concept design phase has been undertaken and after a broad opinion of cost has been offered, a degree of design development is necessary to get the drawings to a point where an approval to develop is sought.
Should the price seem around about the figure you are willing to spend, the pathway to delivering a project beyond concept stage is to make a Development Application with the local authority, for approval to develop, then finish documentation to such a degree of detail as meets the needs of an already selected builder or in much greater detail in order to tender for a competitive price; select and engage a builder, who will then gain a Building Permit for the works. A building permit requires scope of works to be defined by drawings, a form of contract, and a specification. Some builders can do that in-house.
An architect usually delivers a very high degree of detailed documentation (say 10 – 20 A3 pages of drawings) prior to selection and engagement of builder, and administers a traditional fixed price, lump sum contract on your behalf, supervising and endorsing the builder’s requests for payment, observing and supervising your own or the builder’s own requests for variations, and answering all requests for information by way of instructional notes. Records are kept and a tight schedule is maintained, damages are charged for delays and defects if they are not rectified in the agreed manner. It is a safe method.
I can use this methodology if you prefer a managed and supervised process. If you would like me to do so, I would undertake that process, under the observance of a Registered Architect (for no extra cost for that observance).
Alternatively, if you have found and become satisfied with a good builder and that builder wishes not to engage in an architect-administered traditional fixed price, lump sum contract, there are a multitude of other ways to procure a built project. Different builders prefer different contractual arrangements. A builder willing to engage in a lump sum contract is often confident in pricing.
I urge clients to explore a variety of contract types so they can interview builders in a useful way. A Cost-Plus contract, for instance, does not need a great deal of detail in drawings or documents, and one can save money on documentation and expertise; the risk is carried by yourself to convey, select and agree upon each phase of work with the builder; and the cost of each phase is offered plus a pre-agreed margin: cost-plus gives no advance surety of overall price whatsoever. A Design-Construct contract can be procured early (even at concept stage), where the risk is carried by the builder to meet the sum allocated to the scope of works.
I am most willing to hand over as much good and useful information and collaboration as is required for a builder to be confident in delivering a great outcome, whether via traditional architectural documentation, design or site meetings, phone advice/agency, or other drawings, documents or supervision. I am happy to offer an hourly rate of $110 or quote a lump sum for any type of service. I can chair a sequence of builder interviews on behalf of a client.
A useful guide to some contract types is at https://constructioncourses.com.au/understanding-australian-building-contracts/
I hope you find this useful information.