How to assess a NSW duplex feasibility
A duplex feasibility compares the value of two completed dwellings with land, construction, statutory charges, finance, tax and sale costs. A positive result is conditional on the assumptions and a verified planning pathway.
Reviewed 12 September 2026 · General educational guidance
Start with the decision
Are you buying a site to sell both dwellings, or already own a home and want to retain one? The current Feasomate model assumes sale of all dwellings. Do not treat its profit as the outcome of retaining or renting one. For an existing property, ask an adviser to compare incremental cash cost and the opportunity cost of the land separately.
Check planning before relying on yield
The NSW Low and Mid-Rise Housing Policy commenced in stages on 1 July 2024 and 28 February 2025. Location, hazards, exclusions and development standards still matter. A map or an entered FSR does not establish approval. Record the applicable planning instruments, a current 10.7 certificate and advice about DA or CDC eligibility.
Complete the cost stack
Include purchase duty and legal costs, demolition, asbestos, services, design, authority charges, construction, contingency, holding costs, lender fees, interest and selling costs. Check local contributions and the state HPC separately. Use consistent GST-inclusive cost inputs in Feasomate and confirm the selected tax treatment.
Stress the result
Compare a lower sale price and higher build cost together. Review the required sale price, maximum affordable land price and funding peak before sales repay debt. Replace illustrative inputs with dated quotations and settled comparable evidence. Save missing and reviewed evidence alongside the model.
Official sources
NSW Low and Mid-Rise Housing Policy
Project-specific planning and tax advice remains necessary. Read the calculation disclosures.
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