Build, Sell, or Rent Your Duplex — Which Strategy Wins?
Once your duplex is built, you have three core options: sell both, rent both, or sell one and keep one. The right strategy depends on your financial position, tax situation, and long-term goals. Buildana (Lic. 487805C) builds duplexes for investors who pursue each of these strategies. Here is the analysis.
Strategy 1 — Sell Both Dwellings
Best for: Developers seeking a lump-sum profit to reinvest.
Scenario (Fairfield LGA, Torrens title duplex, 2 × 150 sqm): • Total development cost (incl. land, construction, subdivision, holding, selling): $1,870,000 • Sale proceeds: $1,900,000–$2,100,000 • Gross profit: $30,000–$230,000 • Less CGT (if held under 12 months — full rate): significant tax impact • Less GST (if registered for GST — applies if selling new residential premises as a business): 10% on sale price
Advantages: Realises profit immediately. Frees capital for next project. No ongoing management or maintenance.
Risks: Market timing risk — selling into a soft market compresses margins. Transaction costs (agent fees, marketing, legal) consume $40,000–$60,000 of proceeds. CGT and GST can significantly reduce net profit.
Key insight: sell-both works best when you buy land below market value, build efficiently, and sell into a rising market. In a flat or falling market, margins are thin.
Planning a duplex in Sydney?
Free site review — we'll assess zoning, feasibility and likely build cost before you commit to design fees.
Strategy 2 — Rent Both Dwellings
Best for: Long-term wealth builders who already have income to service the construction loan.
Scenario (same Fairfield duplex): • Annual rental income: $57,200–$67,600 (2 × $550–$650/week) • Annual holding costs (interest, rates, insurance, management, maintenance): $62,000–$67,000 • Net income year 1: approximately breakeven
Advantages: Capital growth over time — compounding property value appreciation. No CGT triggered until sale. Rental income increases annually (Western Sydney rental growth: 3–5% per year). Depreciation benefits — new construction generates significant depreciation deductions ($20,000–$30,000/year in years 1–5).
Risks: Cash flow may be negative in early years. Tenant risk and vacancy periods. Interest rate sensitivity. Maintenance costs increase after warranty period.
Key insight: rent-both works when you have other income to support the holding costs and you are focused on 10–20 year wealth building. The equity position (approximately $200,000–$400,000 above cost) provides buffer against market fluctuations.
Strategy 3 — Sell One, Keep One
Best for: Homeowners wanting to live in one and eliminate construction debt, or investors wanting a debt-free rental.
Scenario: • Sell dwelling 1 (Torrens title): $950,000–$1,050,000 • Construction cost (both dwellings): $900,000 • Sale of one dwelling recoups: 100–117% of construction cost • Remaining dwelling: owned outright or with minimal debt • Rental income from dwelling 2 (if not owner-occupied): $550–$650/week = $28,600–$33,800/year
Advantages: De-risks the investment — construction cost is recovered on sale. Ongoing rental income on a fully owned asset. If you live in the other dwelling — no rent, no mortgage on a brand-new home.
Risks: CGT applies to the sold dwelling (but not to the owner-occupied dwelling under CGT main residence exemption). Still requires upfront construction finance.
Key insight: sell-one-keep-one is the most popular strategy among Buildana's duplex clients in Western Sydney. It provides the best balance of risk management, cash recovery, and long-term wealth building.
For the full investment analysis, see our duplex investment ROI guide. For the complete building process, see our complete guide to building a duplex in Sydney. Contact Buildana for a free duplex feasibility assessment.
