Buying a duplex as an investment property gives you two income streams on one title, but lenders treat these properties differently to a standard house or unit.
The loan structure you choose, the deposit you'll need, and how you position the application can all shift depending on whether the duplex sits on one title or two, whether both dwellings are tenanted, and how the lender views rental income from a multi-dwelling asset. Getting this wrong can mean a lower borrowing capacity or a declined application, even when your financial position is strong.
How lenders assess rental income on a duplex
Most lenders will assess 80 per cent of the expected rental income from both dwellings when calculating your borrowing capacity. Some lenders apply a lower shading percentage if only one dwelling is tenanted at the time of application, or if the property is vacant and you're relying on an appraisal rather than a signed lease. Where both dwellings are leased to separate tenants, the income is typically aggregated and then shaded at the lender's standard percentage. A duplex in Croydon with both units leased can generate strong rental income relative to the loan amount, particularly if the property is close to Croydon Station or within walking distance of the Eastfield or Town Park precincts where tenant demand remains consistent.
Single title or subdivided: why it changes your loan options
A duplex on a single title is treated as one residential security by most lenders. You take out one loan, and both dwellings secure that loan. A duplex that has been subdivided into two separate titles is treated as two properties, which means you may need two separate loans or a loan structured across multiple securities. Some lenders will still allow a single loan across both titles if they're part of the same contract, but others treat each title as a standalone investment property, which can affect how much you can borrow and whether lenders mortgage insurance is required. If you're considering a duplex that could be subdivided in the future, your loan structure needs to allow for that without forcing a full refinance. We regularly see buyers overlook this until after settlement, which can limit your options later if you want to sell one dwelling or refinance separately.
Deposit size and LMI on duplex purchases
Most lenders require a minimum 10 per cent deposit for investment loans, though some will lend at 90 per cent LVR with LMI if your financial position supports it. Duplexes are generally treated the same as other residential investment properties in terms of deposit requirements, but some lenders apply stricter serviceability tests or lower maximum LVRs depending on the property type and location. If you're using equity from an existing property to fund the deposit, the lender will assess the combined loan to value ratio across both properties. Lenders mortgage insurance is calculated on the loan amount and LVR, and the premium is added to your loan or paid upfront. On a duplex purchase, LMI can be higher than on a standard investment property if the lender views the asset as having a smaller resale market.
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Interest only or principal and interest for a duplex loan
Most investors choose an interest only loan structure for the first five years to maximise cash flow and tax deductibility. With a duplex, the rental income from both dwellings can often cover or exceed the interest only repayments, depending on your investment loan interest rate and how much you've borrowed. Interest only loans attract a higher risk weighting under APRA's prudential standards, which means lenders apply stricter serviceability buffers. You'll need to demonstrate you can service the loan at a rate at least three percentage points above the actual rate, which can reduce your borrowing capacity compared to a principal and interest structure. If your goal is to build equity quickly or you're planning to hold the duplex long term, a principal and interest loan may offer more flexibility, particularly if you're refinancing down the track and want to demonstrate a lower loan balance.
Variable or fixed rate for a duplex investment
Variable rates give you flexibility to make extra repayments, redraw, or refinance without break costs. Fixed rates lock in your repayments for a set period, which can help with budgeting and cash flow certainty, but you lose flexibility during the fixed term. Some investors split the loan between variable and fixed to balance both. For a duplex investment, the rental income is usually stable enough that a variable rate makes sense, particularly if you're planning to use equity for further purchases or you want the option to pay down the loan ahead of schedule. Fixed rates on investment loans are typically higher than variable rates, and if you fix for three to five years and rates fall, you'll pay break costs to exit early.
Tax treatment and deductibility on duplex investment loans
Interest on your duplex loan is deductible against the rental income from both dwellings, along with other holding costs such as property management, insurance, council rates, and repairs. For properties acquired before 12 May 2026, losses can be offset against your other income, including salary. For established duplexes purchased after that date, losses are only deductible against other residential property income from the 2027-28 income year onward. New build duplexes retain full negative gearing treatment regardless of when they're purchased. If you're considering a duplex in Croydon that's already constructed, the change in deductibility rules may affect your after-tax cash flow depending on your income and other investments. Borrowing costs, including loan establishment fees and LMI premiums, are generally deductible over five years or the loan term, whichever is shorter.
Structuring the loan to allow for future portfolio growth
If the duplex purchase is your first investment property, how you structure the loan now will affect how much you can borrow for your next purchase. Lenders assess your entire debt position when you apply for a new loan, including your existing investment loans and any owner-occupied debt. Keeping your loan structure clean from the start means separating your investment borrowings from any personal or owner-occupied lending, and avoiding cross-collateralisation unless it's necessary to get the deal across the line. A duplex on a single title can be used as security for a standalone loan, with your owner-occupied property kept separate. This gives you the option to refinance the duplex loan later without affecting your home loan, or to release equity from the duplex to fund your next purchase without redrawing from your home.
Preparing your application for a duplex investment loan
Lenders will want to see a rental appraisal or signed lease agreements for both dwellings, along with your standard income verification, asset and liability statements, and a clear explanation of how the purchase fits your investment strategy. If you're relying on equity from another property, the lender will order a valuation on that property as well as the duplex you're purchasing. Body corporate fees, if applicable, will reduce your serviceability, as will any other investment property expenses or personal commitments. Where the duplex is vacant at the time of application, some lenders will only assess rental income at 70 to 75 per cent of the appraised amount until both dwellings are leased. Having a clear plan for how you'll manage vacancy periods and what your cash flow buffer looks like will strengthen your position, particularly if you're borrowing at a higher LVR or already hold other investment property.
Call one of our team or book an appointment at a time that works for you to discuss your duplex investment loan options and get your application structured correctly from the start.
Frequently Asked Questions
Do I need a bigger deposit to buy a duplex as an investment property?
No, most lenders treat a duplex the same as other residential investment properties and require a minimum 10 per cent deposit. Some lenders will lend at 90 per cent LVR with lenders mortgage insurance if your financial position supports it.
How do lenders assess rental income from both dwellings in a duplex?
Lenders typically assess 80 per cent of the expected rental income from both dwellings when calculating your borrowing capacity. If only one dwelling is tenanted or both are vacant, some lenders apply a lower shading percentage or assess the income more conservatively.
Does it matter if the duplex is on one title or two separate titles?
Yes. A duplex on a single title is treated as one residential security with one loan. A subdivided duplex on two titles may require two separate loans or a loan structured across multiple securities, which can affect borrowing capacity and refinancing options.
Is interest on a duplex investment loan tax deductible?
Yes, interest on a duplex investment loan is deductible against the rental income from both dwellings. For properties acquired before 12 May 2026, losses can be offset against other income including salary. For established duplexes purchased after that date, losses are only deductible against other residential property income from the 2027-28 income year.
Should I choose a variable or fixed rate for a duplex investment loan?
Variable rates offer flexibility to make extra repayments or refinance without break costs, which suits most investors. Fixed rates provide repayment certainty but limit flexibility. Some investors split the loan between both to balance cash flow certainty and future options.
