Duplex Investment ROI — Real Numbers for Western Sydney
A duplex development is both a construction project and an investment. Understanding the return on investment (ROI) helps you decide whether to build and how to structure the development. Buildana (Lic. 487805C) has built duplexes for investors across Fairfield, Liverpool, Cumberland and Canterbury-Bankstown. Here are the real numbers.
Development Profit — Build and Sell
Build-and-sell scenario: You own a 600 sqm R2 block in Fairfield LGA. You demolish the existing house and build a Torrens title duplex.
Costs: • Existing property value (opportunity cost): $900,000 • Demolition: $15,000 • Construction (2 × 150 sqm, medium brick veneer): $700,000 • External works: $60,000 • Approval fees: $8,000 • Subdivision (Torrens title): $45,000 • Council contributions: $40,000 • Holding costs (14 months — interest, insurance): $55,000 • Selling costs (agent, marketing × 2): $50,000 • Total project cost: $1,873,000
Revenue: • Sale price dwelling 1: $950,000–$1,050,000 • Sale price dwelling 2: $950,000–$1,050,000 • Total revenue: $1,900,000–$2,100,000
• Development profit: $27,000–$227,000 • ROI: 1.4–12.1% on total project cost
The variation is large because it depends on end sale prices. In a rising market, profits are stronger. In a flat market, margins are thin after all costs are included.
Build-and-Hold — Rental Return
Build-and-hold scenario: You retain both dwellings as investments.
Annual rental income: • Dwelling 1 (3-bed, new): $550–$650/week = $28,600–$33,800/year • Dwelling 2 (3-bed, new): $550–$650/week = $28,600–$33,800/year • Total annual rent: $57,200–$67,600
Annual costs (estimated): • Mortgage interest (on construction loan balance): varies — assume $50,000/year at current rates on $700,000 construction finance • Council rates (× 2): $3,000–$5,000 • Insurance (× 2): $3,000–$4,000 • Maintenance (year 1 — minimal for new build): $2,000–$3,000 • Property management (8% of rent): $4,576–$5,408 • Total costs: $62,576–$67,408
Net income before tax in year 1 is approximately breakeven to slightly negative. However, you own two properties worth $1,900,000–$2,100,000 against a construction cost of $900,000 (land was already owned). The equity position is the value — rental income improves over time as rents increase while the fixed mortgage stays stable.
Maximising Your Duplex ROI
Strategies that improve duplex investment returns:
1. Build on land you already own. Eliminating the land purchase removes the biggest cost and stamp duty. Your construction-only ROI is dramatically higher than when land must be purchased.
2. Torrens title over strata. Torrens title dwellings sell for 5–10 per cent more than strata equivalents. The additional $15,000–$30,000 subdivision cost is recovered many times over.
3. Live in one, rent the other. The owner-occupied dwelling may qualify for CGT exemption. Rental income from the second dwelling services the construction loan.
4. Sell one, keep one. Selling one Torrens title dwelling recoups most or all of your construction cost. You retain the second dwelling as a debt-free or low-debt investment.
5. Optimise dwelling size for the market. In Western Sydney, 3–4 bedroom family homes rent fastest and sell highest. Do not over-build — 150 sqm per dwelling is the sweet spot for most suburbs.
For the full duplex building process, see our comprehensive guide to building a duplex in Sydney. For build-sell-rent strategies, see our build, sell or rent your duplex guide. Contact Buildana for a free duplex feasibility assessment.
