Beginner's Guide to Duplex Investment Loans

A duplex can spread your rental income across two tenants instead of one. That matters when you're rostered on shift work and need rental income you can count on without chasing tenancies every few months.

Most lenders treat a duplex the same as any other residential investment property, but the way they assess rental income and the deposit you'll need can shift depending on whether the duplex sits on one title or two. If you're buying a duplex as your first investment property, you'll need at least 10% deposit plus costs, though some lenders will consider 5% if you're willing to cover Lenders Mortgage Insurance. The calculation changes if you already own property and plan to use equity.

How Lenders Value Rental Income from a Duplex

Lenders typically assess 80% of the combined rental income from both units when calculating how much you can borrow. If one unit rents for $400 per week and the other for $420, the lender will use $656 per week in their serviceability calculation. That discount accounts for vacancy periods, maintenance, and the possibility that one tenant moves out while the other stays.

Consider a Senior Constable earning $95,000 per year who identifies a duplex in Baldivis with both units currently tenanted. Each side rents for $380 per week. The lender assesses $608 per week in rental income, which adds roughly $32,000 to annual income for borrowing purposes. That difference can lift borrowing capacity by around $160,000, depending on other commitments. The duplex is listed at $620,000, and with a 10% deposit plus $18,000 in stamp duty and settlement costs, the total outlay is $80,000. The loan amount sits at $558,000, and because the rental income partially offsets the loan repayments, the serviceability assessment clears without needing a second income.

Single Title or Strata: Which One Affects Your Loan

A duplex on a single freehold title is treated as one property. A duplex on two strata titles is treated as two separate units, even if they share a common wall. Lenders don't usually charge more for one over the other, but strata title adds body corporate fees that reduce your net rental income. Those fees are typically between $800 and $1,500 per year for a basic duplex with shared insurance and common area maintenance.

If you plan to sell one side later and keep the other, strata title gives you that option. If you want full control over both sides without strata involvement, freehold works better. Either way, your investment loan options won't narrow significantly based on title type alone, though some lenders prefer freehold for larger loan amounts.

Deposit Requirements and LMI Waivers for Police

Most lenders require a 10% deposit for an investment loan, which means you'll also pay Lenders Mortgage Insurance on the portion above 80% loan to value ratio. For a $620,000 duplex, a 10% deposit leaves you borrowing 90% of the purchase price, and LMI on that amount typically ranges from $15,000 to $22,000 depending on the lender.

Some lenders offer LMI waivers for police officers up to 90% or even 95% loan to value ratio, which removes that cost entirely. If you're buying your first investment property and already own a home, you may also be able to leverage equity from your existing property instead of saving a new deposit. That approach keeps your cash available for other costs like property management setup, minor repairs, or holding costs if a tenant vacates.

Interest Only or Principal and Interest Repayments

An interest only loan reduces your monthly repayment, which improves cash flow if the rental income doesn't fully cover the loan cost. On a $558,000 loan at current variable rates, an interest only repayment might sit around $2,100 per month compared to $3,200 for principal and interest. That $1,100 difference matters when you're holding the property through a vacancy period or covering unexpected maintenance.

The downside is that you're not reducing the loan balance, so you'll owe the same amount in five years unless property values rise. Some investors prefer principal and interest from the start to build equity faster, particularly if they plan to use that equity to purchase a second investment property later. Others switch from interest only to principal and interest once rental income increases or other debts are cleared. Your repayment structure isn't locked in forever, and you can refinance or restructure as your situation changes.

Negative Gearing and the 2027 Tax Changes

If your duplex costs more to hold than it earns in rent, you're negatively geared. Until 1 July 2027, you can claim that loss against your police salary, which reduces your taxable income. From 1 July 2027, if you purchased an established duplex after 12 May 2026, those losses can only be offset against rental income or capital gains from residential property, not your wages. Losses you can't use this year carry forward to future years, so they're not wasted.

A Sergeant earning $110,000 per year who buys a duplex in Ellenbrook might have $8,000 in net rental losses each year after interest, rates, insurance, and depreciation. Under the old rules, that $8,000 reduces taxable income to $102,000, saving around $3,000 in tax. Under the new rules, that $8,000 can only offset future property income, so the immediate tax benefit disappears. The property still builds equity through capital growth and loan reduction, but the cash flow equation tightens. If you're considering a duplex purchase now, it's worth running the numbers with both scenarios in mind.

How Vacancy Rates Change the Serviceability Calculation

Lenders assume some vacancy when they assess your rental income, but they don't usually specify a vacancy rate as a separate line item. The 80% rental income factor already accounts for it. What changes the calculation is when one side of the duplex sits vacant for an extended period. If you're buying a duplex where one unit is currently untenanted, some lenders will only assess 80% of the rent from the occupied side, which cuts your assessed income in half.

In growth areas like Byford or Brabham, vacancy rates are low and turnaround is quick. In areas with slower demand, a vacant unit might take six to eight weeks to fill, and that gap can stretch your cash flow if you're holding costs on your own. Property management fees, landlord insurance, and a buffer for vacancy periods should all factor into your decision before you sign a contract.

Refinancing an Existing Investment Loan to Buy a Duplex

If you already own an investment property and want to buy a duplex, investment loan refinancing can consolidate debt or release equity. Consider a Constable who bought a unit in Midland three years ago for $350,000 with a $315,000 loan. That property is now worth $400,000, which means there's $85,000 in equity. Refinancing up to 90% of the new valuation releases $45,000 in usable equity, which covers the deposit and most of the purchase costs for a second property.

Some lenders will let you cross-collateralise both properties under one loan, while others prefer separate loans for each property. Cross-collateralisation can simplify your paperwork and sometimes unlock higher borrowing capacity, but it also means both properties secure both loans. If you want to sell one property later without affecting the other loan, separate loans give you more control. Either structure works depending on your long-term plan.

What You'll Need for the Application

Lenders will ask for proof of rental income if the duplex is already tenanted, which usually means a signed lease agreement and a rental appraisal from a licensed property manager. If the duplex isn't tenanted yet, you'll need a rental appraisal showing the expected rent for each side. That appraisal should come from a property manager familiar with the suburb, not a sales agent's estimate.

You'll also need your last two payslips, a recent notice of assessment from the ATO, and details of any other debts or commitments. If you're using equity from another property, the lender will want a recent valuation or rely on an automated valuation model. The whole process from application to settlement typically takes four to six weeks, depending on how quickly you can supply documents and whether the lender needs a physical valuation.

Call one of our team or book an appointment at a time that works for you. We'll run the numbers, confirm which lenders offer LMI waivers for WA Police, and make sure the rental income assessment works in your favour before you put in an offer.

Frequently Asked Questions