Unlock the secrets to financing a duplex investment

What Makes a Duplex Investment Loan Different from a Standard Home Loan

Investment loans differ from home loans because the property generates rental income, which lenders assess differently to owner-occupied properties. When you apply for finance to purchase a duplex in Merrylands, the lender looks at the rental income from both dwellings, your personal income, and your ability to service the loan even if one or both units sit vacant for a period.

Consider a buyer who finds a duplex on Railway Parade, close to Merrylands Station. Both units are currently tenanted, bringing in a combined rental income. The lender will calculate how much of that rental income they can use in the assessment, typically around 80%, to allow for vacancy periods and maintenance costs. They'll also apply a higher interest rate buffer than they would for an owner-occupied loan, which means you need to prove you can still afford repayments if rates rise by around 3%.

The deposit required for an investment property is typically higher than for an owner-occupied home, with most lenders requiring at least 10% to 20% of the purchase price. If you're borrowing more than 80% of the property value, you'll pay Lenders Mortgage Insurance, which protects the lender if you default on the loan. This insurance cost is usually added to your loan amount rather than paid upfront.

How Lenders Assess Rental Income from a Duplex

Lenders calculate your borrowing capacity using a percentage of the expected rental income, not the full amount. If your duplex generates rental income that totals around what similar properties in Merrylands achieve, the lender will take that figure, apply a discount to account for vacancy, and add it to your other income sources when working out how much you can borrow.

The rental yield in Merrylands has historically been solid due to the suburb's affordability and proximity to Parramatta and the city. Properties near Merrylands Station or close to schools and Stockland Merrylands shopping centre tend to attract consistent tenant demand. Lenders know this, but they still apply conservative vacancy rates because rental markets can shift.

If both units in the duplex are identical in size and finish, lenders assume similar rental income for each. If one unit is larger or has been renovated, they'll look at comparable rentals in the area to estimate what each side could achieve. This is why having a rental appraisal from a local agent can help, even before you make an offer on the property.

Interest Only vs Principal and Interest for Duplex Investments

Interest-only loans allow you to pay only the interest portion of the loan for a set period, typically five years, which reduces your monthly repayments but does not reduce the loan balance. Many investors choose this structure because it keeps costs lower while the property generates rental income and, over time, grows in value.

In a scenario like this: you purchase a duplex, both units are tenanted, and you're using the rental income to cover most of the loan repayments. An interest-only loan means your monthly costs are lower, which can help if the rental income fluctuates or if you need to cover maintenance or strata fees for the shared driveway or common areas. After the interest-only period ends, the loan converts to principal and interest, and your repayments increase because you're now paying down the loan balance as well.

Principal and interest loans reduce your loan balance over time, building equity in the property, but require higher monthly repayments. Some investors prefer this approach because it means they're actively reducing debt and building equity, which can be useful if they plan to refinance or leverage that equity to purchase another property down the line. You can read more about leveraging equity to expand your portfolio.

Tax Considerations When Financing a Duplex Investment

Under current rules, if you purchased your duplex before 13 May 2026, you can claim the full annual loss from your investment property against your other income, including your salary. If your loan repayments, council rates, strata fees, insurance, and maintenance add up to more than the rental income you receive, that shortfall can reduce your taxable income.

If you're purchasing an established duplex after 12 May 2026, the rules change from 1 July 2027. Losses from the property can only be offset against rental income or capital gains from other residential properties, not against your wage income. You can still carry forward those losses to use in future years, but the immediate tax benefit is different. This doesn't apply if you're buying a new duplex or one that's part of an affordable housing program.

When you eventually sell the duplex, capital gains tax applies to any profit you make. For properties purchased before the rule changes, the 50% discount on capital gains still applies if you've held the property for more than 12 months. For new purchases after 12 May 2026, a new system based on inflation indexing and a minimum 30% tax on gains will apply from 1 July 2027, but you'll only pay tax on gains that occur after that date. If you're buying a newly constructed duplex, you can choose whichever method is more favourable.

These changes don't affect the main residence exemption, so if you were to move into one side of the duplex and treat it as your home, different rules would apply. Speaking to a tax adviser or accountant before committing to a purchase helps you understand how the numbers work for your specific situation. Understanding the tax benefits of investment property can help you structure your finances in a way that works for you.

What Happens If One Unit in the Duplex Is Vacant

Lenders assume a vacancy rate when they assess your loan, but if one unit sits empty for longer than expected, you need to cover the full loan repayment from your own income. This is why lenders apply a buffer when calculating serviceability. They want to know you can still afford the loan if rental income drops or disappears temporarily.

In Merrylands, vacancy periods tend to be short because the suburb has strong transport links, schools, and shopping, which keeps tenant demand consistent. But if a tenant leaves and the property needs repairs or a fresh coat of paint before re-listing, you might have a gap of a few weeks or even a couple of months. If you've structured your loan with a buffer and kept some savings aside for this situation, it's manageable. If you've stretched your borrowing capacity to the limit, a vacancy can put you under pressure.

Some investors set up an offset account linked to their investment loan and keep a few months' worth of repayments in there. The balance in the offset reduces the interest you pay, and it's there if you need it to cover a shortfall. This is a feature worth asking about when you're comparing investment loan options.

Refinancing an Existing Duplex Investment Loan

Refinancing allows you to switch lenders or loan products to access a better interest rate, different loan features, or release equity for another investment. If you purchased your duplex a few years ago and the property has increased in value, refinancing can give you access to that equity without selling the property.

For example, if you bought a duplex and the value has since increased, refinancing lets you borrow against that increased value. You could use the additional funds as a deposit for another investment property or to renovate one or both units to increase rental income. Investment loan refinancing can also help if your current lender's rates have crept up or if your financial situation has changed and you need more flexibility.

Refinancing does come with costs, including discharge fees from your current lender, application fees for the new loan, and possibly valuation fees. You need to weigh these costs against the benefit you're getting from the new loan. If the interest rate saving or the equity release is significant, refinancing makes sense. If the benefit is marginal, it might not be worth the hassle.

Call one of our team or book an appointment at a time that works for you. We can walk through your current loan, compare it to what's available now, and show you whether refinancing would put you in a stronger position.

Frequently Asked Questions