Duplex Rental Yield Calculator

How the duplex yield numbers work

Duplex development is the most common multi-dwelling residential investment in Western Sydney — since the July 2024 NSW dual-occupancy reform made dual-occ permissible in most R2 zones, the number of duplex DAs lodged with Fairfield, Liverpool, Cumberland, Canterbury-Bankstown and Blacktown councils has roughly doubled. The calculator above runs the same yield model Buildana uses internally before quoting a duplex client: gross yield on total project cost (land + build + fees + holding), net yield after expenses, and weekly cash-flow position.

Inputs that drive the result. Land cost is the single biggest lever — a $50k swing on the block changes gross yield by roughly a quarter of a percentage point. Build cost defaults to 2026 Western Sydney rates of $2,500–$3,200 per m² (Rawlinsons-derived, reconciled against our own duplex project actuals); override per-m² if you have a specific quote. Council Section 7.11/7.12 contributions, demolition, site works and approvals are pre-loaded by LGA. Weekly rent uses CoreLogic and Rent Bond Board medians indexed quarterly; new builds typically command a 5–15% premium over the suburb median for the equivalent dwelling configuration.

What the calculator doesn’t do. It doesn’t model the hold-vs-sell decision (the Feasibility Check covers that). It doesn’t deduct strata levies on Strata-titled duplex builds ($2,000–$4,000/yr/dwelling). It doesn’t model capital gains tax, depreciation, negative gearing or financing structure — those vary by individual circumstance. Used with realistic inputs, expect ±10% accuracy on net yield against a real duplex operating fully tenanted after 12 months.