Duplex Purchase Loans & What Not to Overlook

A duplex purchase sits somewhere between buying a standard house and an investment property in terms of how lenders assess it.

If you're planning to occupy one side and rent the other, lenders treat the loan as owner-occupied but price in the rental income when calculating serviceability. If both sides are rented, it becomes an investment loan with different rate structures and deposit requirements. The distinction affects your interest rate, your loan to value ratio, and whether certain lender products remain available to you.

How Lenders Assess a Duplex Purchase

Lenders assess a duplex based on how you intend to use the property, not just the fact that it has two dwellings. If you're living in one side and renting the other, most lenders will classify the loan as owner-occupied and allow you to access owner-occupied rates. The rental income from the second dwelling usually gets factored into your serviceability at around 70% to 80% of the gross rent, which can increase your borrowing capacity compared to purchasing a single dwelling.

Consider a software developer purchasing a duplex where one side will be owner-occupied and the other rented for $450 per week. The lender applies the owner-occupied interest rate to the entire loan but adds around $315 to $360 per week to the serviceability calculation, effectively reducing the net cost of the mortgage in the lender's assessment. This can allow you to borrow more than you would for a standalone house at the same purchase price, even though the ongoing holding costs are lower due to the rental offset.

If both sides are rented from settlement, the loan is classified as an investment loan. You'll pay a higher interest rate, typically 0.30% to 0.60% above the equivalent owner-occupied rate, and lenders may require a larger deposit depending on your loan to value ratio. Some lenders also apply different serviceability buffers to investment loans, which can reduce how much you're able to borrow.

Loan Structure for Mixed-Use Duplex Ownership

When you occupy one side and rent the other, your loan structure needs to reflect the split between personal use and income-generating use. Most borrowers in this situation use a split loan, with one portion set up as owner-occupied and linked to an offset account, and the other portion structured as investment to maximise tax deductions on the interest attributable to the rented side.

The split doesn't need to be 50/50. You can allocate the loan based on the relative value of each dwelling if they differ in size or configuration, or split it evenly if they're identical. The investment portion allows you to claim the interest as a deduction, while the owner-occupied portion benefits from the lower rate and can be paid down faster using an offset account linked to your salary.

In our experience, developers who treat the duplex as a medium-term hold often structure the owner-occupied portion as variable with full offset and the investment portion as fixed for two to three years. This gives you the flexibility to pay down the non-deductible debt while locking in a rate on the portion you want to keep stable for tax planning. You can find more detail on how this type of structure works in our guide to interest-only loans for tech industry workers.

Valuation and Title Structure Complications

Duplexes on a single title are usually valued as one property, even if each dwelling could be separately tenanted. Lenders rely on this single valuation to determine your loan to value ratio and decide whether Lenders Mortgage Insurance applies. If the valuation comes in lower than the purchase price, you may need to increase your deposit or renegotiate the contract.

Duplexes on separate titles, often called dual-occupancy on subdivided lots, are treated as two distinct properties. Some lenders will value them separately and allow you to use one as security for the other, but this can complicate the loan structure and may require cross-collateralisation. If you're planning to sell one side in the future, having them on separate titles makes that process more straightforward, but it also means you may need to meet serviceability requirements for two loans instead of one.

Title structure also affects your ability to access certain loan products. A duplex on a single title may not be eligible for some first home buyer schemes or low-deposit programs that restrict lending to properties under a certain land size or exclude multi-dwelling configurations. If you're relying on low-deposit loans for tech industry workers or an LMI waiver, confirm early in the process that the property type is accepted by your intended lender.

Offset Accounts and Loan Features for Duplex Buyers

Most lenders allow you to link an offset account to the owner-occupied portion of a split loan, but not always to the investment portion. The reason is tax-related: if you offset the balance on an investment loan, you reduce the interest charged, which in turn reduces the amount you can claim as a deduction. For that reason, many buyers only attach an offset to the owner-occupied split and allow the investment portion to accrue interest in full.

If you want the flexibility to redraw or access equity later without refinancing, choose a variable rate home loan with redraw on both splits. Some lenders restrict redraw on fixed-rate splits or charge a fee to access it, so confirm the loan features before you lock in the structure. You can compare how different lenders handle loan features in our breakdown of home loan options.

Portability is another feature worth considering if you think you might move before selling the duplex. A portable loan allows you to transfer the existing loan to a new property without breaking your fixed rate or losing your offset account. Not all lenders offer this, and those that do often apply conditions around loan to value ratio and property type.

When Rental Income Affects Your Application

If you're applying for a loan where one side of the duplex will be rented, lenders will ask for evidence that the rental income is realistic. This usually means providing a rental appraisal from a licensed agent in the area where the property is located. The appraisal should be recent, ideally dated within the last 30 days, and should specify the expected weekly rent for the dwelling you intend to lease.

Lenders typically apply a shading factor of 20% to 30% to the rental income, meaning they'll only count 70% to 80% of the stated rent in their serviceability assessment. If the appraisal says $500 per week, the lender might only credit you with $350 to $400 per week when calculating whether you can afford the loan. The shading accounts for vacancy periods, maintenance costs, and the possibility that the rent might not be achieved immediately.

If you're purchasing the duplex as a straight investment with both sides rented, lenders will usually require a rental appraisal for each dwelling and apply the same shading to both. The income is then added to your other earnings when calculating serviceability, but the loan itself is assessed at investment rates. For borrowers with variable income structures like equity or bonuses, the rental income can help smooth out serviceability concerns. More on how lenders treat non-salary income in our article on home loans for commission earners.

Deposit Requirements and LMI for Duplex Purchases

Deposit requirements for a duplex purchase depend on whether the loan is classified as owner-occupied or investment, and whether the property is on a single title or subdivided. For an owner-occupied duplex on a single title, most lenders will lend up to 95% of the property value if you're willing to pay Lenders Mortgage Insurance, though some may cap it at 90% depending on the property size or location.

For investment loans or properties on separate titles, lenders are generally more conservative. Many will require at least a 10% deposit, and some cap lending at 90% even with LMI. If you're using LMI waivers for tech industry workers, confirm whether the waiver applies to multi-dwelling properties, as some lenders exclude them from their professional package offers.

Genuine savings requirements also apply. If you're borrowing above 90% of the property value, most lenders will want to see that at least 5% of the purchase price has been held in your account for three months or longer. Equity from a vesting event, a recent bonus, or funds from a sale are often accepted, but the lender will ask for documentation showing the source and timing of the deposit.

Call one of our team or book an appointment at a time that works for you to discuss how your deposit and income structure align with the loan options available for your duplex purchase.

Frequently Asked Questions