ROI calculator
Granny Flat ROI: How to Work Out If a Backyard Rental Stacks Up
A granny flat can look attractive on paper, but the numbers only make sense once you compare build costs, rent, finance, vacancy, site works and approval-related extras.
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The simplest way to compare a granny flat investment is to start with a rough return-on-investment check before getting emotionally attached to a design. You do not need perfect numbers at the start, but you do need a realistic structure.
The numbers to check first
- Total project cost, not just the advertised building price
- Site works, services, delivery, crane and connection allowances
- Likely weekly rent after a vacancy allowance
- Finance repayments or opportunity cost of cash
- Insurance, maintenance and management costs
- Approval, drafting, engineering, certification and professional advice costs
Why the first estimate is usually too low
Many early budgets miss site-specific costs. Access, slope, drainage, sewer/water connection, electrical distance, bushfire requirements, vegetation overlays and energy-rating upgrades can all affect the real number.
Use a quick calculator before requesting quotes
The free ROI calculator gives a fast way to compare rough cashflow, rent, repayments, yield and payback. The paid Starter Pack adds the more detailed Excel workbook and planning worksheets.
If you are still choosing a layout, compare floor plans before you lock in the numbers. You can start with the internal floor plans page, or browse our floor-plan partner: Australian floor plans partner.
QLD starter course
Before you spend money, check the numbers first
The QLD Granny Flat Investor Starter Course walks through the early checks, budget thinking, ROI questions and quote preparation steps before you commit to plans or suppliers.