What our analysis shows
Our calculations, data as of 23 October 2026
- A standard 60 m² two-bedroom flat comes to $220,000 turnkey in Sydney ($193,500–$246,500) and $187,600 in regional NSW. Construction is about 82% of the bill; the rest is site, connections, approval and the council contribution.
- Granny flats rent for less than apartments. In 81,668 NSW bonds lodged July–September 2026, a one-bedroom detached dwelling in Greater Sydney rented for a median $550 a week, 24% below a one-bedroom flat ($719). Two bedrooms: $650 against $837.
- Using apartment rents to justify the build moves the Sydney payback from 10.7 to 8.3 years. Builder guides we reviewed quote Sydney two-bedroom granny flat rents of up to $780 a week; the bond median is $650.
- Outside Sydney the discount mostly disappears: 2% on the Central Coast and 4% in the rest of the state for one bedroom. Newcastle is the best payback in NSW in our model, at 9.3 years, because the regional build costs less and two-bedroom detached rents are high.
Fastest payback in NSW, 60 m² two-bedroom flat
- Newcastle9.3 years
- Wollongong10.0 years
- Greater Sydney10.7 years
- Hills and north-west10.9 years
- Central Coast10.9 years
- Rest of NSW11.5 years
- Western Sydney12.5 years
- South-west Sydney14.0 years
After agent fees, insurance, maintenance and tax at 30%, no loan. Rent: median of new bonds for detached 2-bedroom dwellings, July–September 2026.
Where the money goes
Our Sydney reference flat, line by line, with the same figures the calculator uses.
| Line | Sydney | Share |
|---|---|---|
| Construction | $180,000 | 82% |
| Site preparation (flat, easy access) | $12,000 | 5% |
| Sewer, water, power and stormwater connections | $10,000 | 5% |
| Design, engineering and BASIX certificate | $8,000 | 4% |
| Approval: Complying development certificate (CDC) | $4,500 | 2% |
| Council s7.11 contribution (typical) | $5,500 | 3% |
| Total | $220,000 | 100% |
Granny flat builders in Sydney often advertise "from $150,000". That figure usually covers construction and the CDC only. The site work, sewer connection and council contribution, about $36,000 on a straightforward block, are quoted separately or as provisional sums. Ask for a fixed price on each before you compare builders.
| Size | Budget | Standard | Premium | Standard, regional |
|---|---|---|---|---|
| Studio, 35 m² | $133,500 | $154,500 | $188,800 | $133,800 |
| 1 bed, 45 m² | $153,600 | $179,100 | $220,800 | $154,000 |
| 2 bed, 60 m² | $187,000 | $220,000 | $274,000 | $187,600 |
Council contributions
Most Sydney councils charge a development contribution on a new secondary dwelling, either a set amount per dwelling under a section 7.11 plan or a percentage of the development cost under a section 7.12 plan, usually 1%. Each council publishes its own rates, and they differ by precinct and often by bedroom count. Canterbury-Bankstown's 2022 plan, for example, charged $5,646 for a studio or one-bedroom secondary dwelling and $9,042 for two bedrooms outside its town centres in the March 2026 quarter. A 1% section 7.12 levy on our reference flat would be about $2,145.
Our model uses a typical $5,500. Your council's figure can be nil or several times that, so look up its contributions plan before you compare quotes; it is the one line builders never include.
The rent you can actually get
NSW Fair Trading publishes every new rental bond with its postcode, dwelling type and bedroom count. We took all 81,668 bonds lodged in July, August and September 2026 and compared detached one- and two-bedroom dwellings, the category granny flats fall into, with flats and units of the same size.
| Area | 1-bed detached | 1-bed flat | Gap | 2-bed detached | 2-bed flat |
|---|---|---|---|---|---|
| Greater Sydney (1166 bonds) | $550 | $719 | 24% | $650 | $837 |
| Western Sydney (263 bonds) | $450 | $580 | 22% | $560 | $640 |
| South-west Sydney (82 bonds) | $440 | $420 | -5% | $500 | $520 |
| Hills and north-west (37 bonds) | $480 | $650 | 26% | $640 | $750 |
| Newcastle (92 bonds) | $400 | $450 | 11% | $640 | $610 |
| Wollongong (41 bonds) | $460 | $480 | 4% | $600 | $600 |
| Central Coast (106 bonds) | $420 | $430 | 2% | $550 | $575 |
| Rest of NSW (661 bonds) | $380 | $395 | 4% | $520 | $500 |
Not every detached one-bedroom dwelling is a granny flat, but in Sydney most are, because one-bedroom houses are otherwise rare. Tenants pay less for a flat that shares a driveway and garden with the owner's family than for an apartment near a station. Price your rent from this table or from an agent's appraisal of comparable granny flats, not from apartment listings.
Bond data: NSW Government rental bond data. Medians of new bonds; groups with fewer than 30 bonds are left out.
If you borrow to build
The payback ranking above assumes you pay cash. Most owners borrow against the house. With the whole build on a 30-year loan at 6.2%, interest is deductible against the rent, and this is what is left each year after interest, running costs and tax, before principal repayments:
| Area | Interest a year | Cash left after tax |
|---|---|---|
| Newcastle | $11,631 | $11,996 |
| Wollongong | $11,631 | $10,704 |
| Greater Sydney | $13,640 | $10,984 |
| Hills and north-west | $13,640 | $10,661 |
| Central Coast | $11,631 | $9,089 |
| Rest of NSW | $11,631 | $8,120 |
| Western Sydney | $13,640 | $8,076 |
| South-west Sydney | $13,640 | $6,138 |
Every area stays positive, but in South-west Sydney the margin is thin. Renting the flat also affects tax on your home: part of a later sale can attract capital gains tax, and a 2025 tribunal decision has narrowed the NSW land tax exemption for detached rented flats. See capital gains tax and land tax.
CDC or DA
A complying development certificate from a private certifier is the normal route: our model allows $4,500 and certifiers typically decide in 10–20 days. A development application to council costs about $7,500 more in fees and reports and usually takes two to four months. You need a DA when the lot is under 450 m² or narrower than 12 m at the building line, when it is a heritage item, when it is rated BAL-40 or flame zone for bushfire, or when the flat would sit in a high-hazard flood area. Lower bushfire ratings and most flood-control lots can still use a CDC with extra conditions. The rules checker covers the main tests.
Steps specific to NSW
Three NSW requirements shape the paperwork. A BASIX certificate sets water and energy targets for the flat, which usually means a rainwater tank or water-efficient fittings and a heat-pump or solar hot water system. Sydney Water must approve the building plans where the flat sits near a sewer main, and building over one can require concrete encasement or a diversion, so get the sewer service diagram before anyone draws. And the builder's Home Building Compensation Fund cover, required on work over $20,000, must be in place before you pay a deposit; other states have their own versions of this insurance.
This week's worked example
Week of 19 October 2026. A new example, rule and owner report every Monday.
A 40 m² one-bedroom flat with a standard finish on a steep block, services 30 m from the house, in Wollongong: our model puts it at $183,600 turnkey ($161,500–$205,500), or $4,590 per m². At the area's median 1-bedroom bond rent of $460 a week it would return 10.2% net and pay back in 12.8 years after tax.
Rule check: Section 50 of the NSW Housing SEPP applies the secondary dwelling rules only where the local plan permits a dwelling house on the land, which is why some R4 high-density lots cannot take a granny flat.
From an owner (NSW, 2023): A buyer walked away from a Liverpool house whose granny flat had been built from an old carport and workshop on the boundary without approval.