Understanding the basics of duplex investment loans

A duplex lets you hold two income streams under one title, which can mean lower entry costs and fewer body corporate complications than buying two separate units.

For Hobart buyers, particularly medical professionals with consistent income but limited time to manage multiple properties, a duplex can deliver rental diversification without the complexity of a scattered portfolio. The lending approach differs from a standard investment loan because lenders treat the property as a single asset, but your income and risk profile changes when you're collecting rent from two tenancies instead of one.

How lenders assess a duplex differently from a single dwelling

Lenders calculate your borrowing capacity using rental income from both dwellings, but they apply a shading factor to account for vacancy and maintenance costs. Most lenders assume 80 per cent of the combined rental income is available to service the loan, which means a duplex generating $900 per week across both tenancies would contribute $720 per week to your serviceability assessment. That buffer protects you if one tenant leaves, but it also reduces the loan amount you can access compared to using the full rental figure.

Consider a GP in Sandy Bay looking at a duplex near the Royal Hobart Hospital precinct. Each side rents for $450 per week, giving a combined income of $900. The lender applies the 80 per cent shading, which brings the recognised income to $720 per week. If the buyer earns $180,000 annually and has no other debt, the shaded rental income is enough to support a loan in the vicinity of $650,000 to $700,000, depending on the lender's serviceability buffer and the buyer's other expenses. Without the rental income, the same buyer might only qualify for $550,000 to $600,000 based on salary alone. The duplex structure directly expands the borrowing range.

Deposit requirements and LMI for duplex purchases

Most lenders require a 20 per cent deposit to avoid Lenders Mortgage Insurance on investment loans where the LVR exceeds 80 per cent. If you proceed with a smaller deposit, LMI is calculated on the full loan amount and adds several thousand dollars to your upfront costs. The premium scales with the LVR, so a 15 per cent deposit will cost more in LMI than an 18 per cent deposit on the same property.

Some lenders allow you to use equity from your home to cover the deposit and costs, which keeps your cash reserves intact. If your Hobart home is worth $750,000 and you owe $300,000, you have $450,000 in equity. A lender may let you borrow up to 80 per cent of your home's value, which is $600,000, leaving $300,000 in usable equity after accounting for your existing loan. That equity can fund the deposit, stamp duty and settlement costs on the duplex without touching your savings. The trade-off is that your home now secures both loans, so if the duplex underperforms or you face financial pressure, both properties are at risk.

Interest only or principal and interest repayments

An interest-only loan keeps your monthly repayments lower, which can improve cash flow if the rental income doesn't fully cover the loan. The downside is that you're not reducing the debt, so your equity position only improves if the property value rises. Principal and interest repayments cost more each month but build equity over time, which gives you a buffer if the market softens or you need to refinance.

From the 2027-28 income year, losses related to established residential investment properties acquired after 7:30pm AEST on 12 May 2026 are deductible only against other income from residential properties, including capital gains on residential properties. If you buy an established duplex now, you can still claim the full loss against your salary until you sell the property, because the grandfathering provisions apply to properties held or under contract before that date. If you're looking at a new build or a property acquired after mid-May 2026, the same tax treatment applies only if the duplex qualifies as an eligible new build under the legislation.

For a Hobart nurse practitioner earning $120,000 and holding an interest-only loan on a duplex with rental income slightly below the interest cost, the ability to offset the loss against salary makes a material difference. Once the new rules apply to non-grandfathered properties, that loss can only reduce tax on other residential property income, which limits the immediate tax benefit unless you already own other investment properties or plan to sell and realise a gain.

Capital gains tax changes from July 2027

From 1 July 2027, the 50 per cent CGT discount for individuals, trusts and partnerships on affected assets is replaced by cost base indexation using CPI and a 30 per cent minimum tax rate on real capital gains accruing from that date. If you buy a duplex today and sell it in ten years, the portion of the gain that accrued before 1 July 2027 is taxed under the current 50 per cent discount rules, and the portion after that date is taxed using the new indexed cost base method.

The indexed cost base approach means you only pay tax on the gain above inflation. If you buy a duplex for $700,000 in late 2026 and it's worth $750,000 on 1 July 2027, the $50,000 gain from that period is taxed using the 50 per cent discount. If the property is then sold in 2032 for $900,000, the $150,000 gain from July 2027 to the sale date is indexed for inflation, and you pay tax only on the real gain. The 30 per cent minimum rate applies if your marginal rate would result in a lower effective tax on that portion. For high-income medical professionals, the minimum rate is unlikely to apply because their marginal rate typically exceeds 30 per cent.

Fixed or variable rate for duplex investment loans

A variable rate lets you make extra repayments and access offset accounts, which can reduce the interest you pay if you park rental income or surplus cash in the offset. A fixed rate locks in your repayment for a set period, usually one to five years, which can protect you if rates rise but removes flexibility. Most lenders don't allow extra repayments on fixed loans without triggering break costs, and offset accounts are rarely available on fixed investment loans.

In our experience, Hobart investors with fluctuating income, such as locum doctors or specialists with private practice income, benefit from the flexibility of a variable loan with an offset. Rental income from both tenancies can sit in the offset and reduce the interest charged daily, which improves cash flow without requiring you to pay down the principal and lose access to the funds.

Why duplex investors in Hobart are choosing split loan structures

A split loan divides your borrowing into two separate accounts, each with its own rate type and repayment structure. You might fix half the loan to protect against rate increases and leave the other half variable to keep access to an offset and repayment flexibility. The split also lets you test both strategies without committing fully to either.

For a duplex in Glenorchy or Moonah, where rental demand from hospital staff and university workers stays relatively stable, a 50/50 split can provide certainty on half your repayments while keeping enough flexibility to absorb extra cash flow or make lump sum payments when rental income exceeds expectations. The fixed portion acts as a baseline cost, and the variable portion adjusts with your financial situation.

Borrowing capacity limits from February 2026

APRA activated a DTI lending limit on 27 November 2025, effective from 1 February 2026, applying to all ADIs. Each ADI may lend, measured on a quarterly basis, up to 20 per cent of new investor loans and up to 20 per cent of new owner-occupier loans to borrowers with a total DTI ratio of six times or greater. If your total debt, including your home loan and the new investment loan, exceeds six times your gross income, the lender may decline the application or require a larger deposit to bring the ratio down.

For a Hobart specialist earning $200,000 and holding a $400,000 home loan, the DTI ratio is 2:1. If the duplex loan adds another $600,000, the total debt is $1 million, which gives a DTI of 5:1. That sits below the six times threshold, so the application proceeds without restriction. If the same buyer wanted to borrow $800,000 for the duplex, the total debt would be $1.2 million and the DTI would be 6:1, which puts the application at the edge of the limit. Some lenders will approve it, but others may ask for a larger deposit or additional income evidence to reduce the ratio.

When to consider refinancing an existing loan before buying a duplex

If your current home loan has a high interest rate or limited features, refinancing before you apply for the duplex loan can improve your borrowing capacity and reduce your overall interest cost. A lower rate on your existing debt means more of your income is available to service the new loan, which can increase the amount a lender is willing to offer.

Refinancing also lets you access equity without cross-collateralising your loans. Instead of using your home as security for both loans through the same lender, you can refinance your home with one lender, release equity as cash, and then use that cash as a deposit with a different lender for the duplex. That keeps the two properties separate, which makes it simpler to sell or refinance either property later without needing consent from both lenders.

Call one of our team or book an appointment at a time that works for you. We'll review your current loans, compare your investment loan options across lenders, and structure the duplex finance in a way that fits your income, your timeline, and the way you want to build your portfolio in Hobart.

Frequently Asked Questions