Avoid These 7 Mistakes When Buying an Investment Unit

The rules changed in June, and they changed again in July.

If you are looking at buying an investment unit in Rouse Hill, you need to know what still works and what does not. The quarantined loss rules start in July next year, and most investors buying established units right now will lose the ability to offset rental losses against their wage. That shifts the type of property that makes sense, the deposit you will need, and whether you should be looking at units at all.

Mistake 1: Assuming You Can Still Negative Gear an Established Unit

Under the rules that take effect from 1 July 2027, net rental losses from residential dwellings acquired on or after 7:30pm AEST on 12 May 2026 are quarantined and can only be offset against other residential rental income or carried forward to offset future residential rental income or future residential property capital gains. If you buy an established unit in Rouse Hill after that date, you cannot offset the loss against your salary. Losses cannot be offset against salary, wages or other non-residential income.

This does not mean you cannot buy an established unit. It means the numbers need to stack up differently. You need more rental income relative to the loan amount, or you need a bigger deposit to lower the interest cost, or both. In our experience, investors who would have been comfortable with a 10 per cent deposit and a $15,000 annual shortfall are now looking at 20 per cent deposits or turning to new builds where the old rules still apply.

Consider a buyer who signs a contract in August this year for a two-bedroom unit near Rouse Hill Town Centre. Purchase price sits at the current unit median for the suburb. They put down 10 per cent and borrow the rest on an interest-only basis at a variable rate. Rent covers about 70 per cent of the interest. Under the transitional rules, they can still claim the full loss against their wage until 30 June 2027. After that, the loss gets quarantined. If they are a PAYG employee on $110,000, that quarantine costs them roughly $4,500 in tax every year compared to what they would have saved under the old system. The property still builds equity and still generates passive income over time, but the annual cashflow is worse and that affects how much they can borrow for the next purchase.

Mistake 2: Ignoring Body Corporate Costs When Calculating Rental Yield

Rouse Hill has a large supply of newer units, many built in the last decade as part of the North West Priority Growth Area. Body corporate fees in complexes with lifts, gyms and secure parking typically sit between $1,200 and $2,000 per quarter. That is $4,800 to $8,000 per year before you pay council rates, water, insurance or any maintenance.

If your gross rental income is $32,000 and your body corporate alone is $6,000, you have just lost nearly 19 per cent of your income before interest. When you add the other holding costs, you are often looking at a net position that is uncomfortably tight, particularly if you are borrowing at a loan to value ratio above 80 per cent and paying Lenders Mortgage Insurance on top.

When we look at the numbers with buyers, we start with net rent after all claimable expenses, not gross. The difference between a complex with a $1,200 quarterly fee and one with a $2,000 quarterly fee is $3,200 per year. Over a ten-year hold, that is $32,000 in additional outgoings. If the unit with the higher fee does not deliver materially stronger capital growth or lower vacancy, it is costing you money for amenities your tenant may not value.

Mistake 3: Borrowing the Maximum Without Accounting for Vacancy

Vacancy rates in Rouse Hill have been low, but they are not zero. The suburb has seen consistent residential construction, and when multiple projects settle in the same quarter, rental supply can spike. If your loan is structured so that you can only meet repayments when the property is tenanted, a four-week vacancy becomes a problem that eats into savings or forces you to rely on credit.

APRA's mortgage serviceability buffer is set at 3 percentage points above the product rate, and lenders apply that buffer when they assess your application. But the buffer tests whether you can service the loan at a higher rate, not whether you can service it with no rental income for a month or two. You need to build that margin yourself.

As an example, if your interest-only repayment is $2,600 per month and your rent is $2,800, you have $200 of headroom. A single vacancy wipes out ten months of that surplus. If you structure the loan with a slightly lower borrowing amount or a larger offset account, you create room to absorb the gap without stress.

Mistake 4: Not Comparing Interest Only and Principal and Interest Structures

Most investors default to interest-only loans because the repayments are lower and the interest is fully deductible. That works when you plan to sell within five to ten years or when you expect strong capital growth to do the heavy lifting. But interest-only periods typically run for one to five years, and when the loan converts to principal and interest, your repayment can jump by 30 to 40 per cent.

If you are buying under the new rules and cannot offset losses, that jump in repayment hits harder because you are funding it entirely from after-tax income. Some buyers are now choosing principal and interest from the start because it forces equity build and reduces the loan balance faster, which lowers the interest cost over time and improves the cashflow position when they come to refinance or purchase again.

There is no universal answer. It depends on your income, your other debts, how long you plan to hold the property, and whether you are building a portfolio or buying a single investment. What matters is that you model both structures with realistic rental income and realistic holding costs before you commit.

Mistake 5: Overlooking the Debt-to-Income Cap When Planning Your Next Purchase

Effective 1 February 2026, ADIs may fund up to 20 per cent of new investor loans at a debt-to-income ratio of 6 times or greater. That cap is applied at portfolio level, which means if a lender has already written a lot of high-DTI investor loans in a given quarter, they may decline yours even if you meet all other criteria.

If you are earning $120,000 and you already have $400,000 in investment debt, adding another $400,000 puts you at a DTI of 6.67. Some lenders will still approve that, but it limits your options and often means you pay a higher rate or accept less flexible loan features. If your strategy involves buying multiple properties over the next few years, each purchase needs to leave enough serviceability for the next one.

This is particularly relevant in Rouse Hill, where unit values have been rising but are still below the median house price in surrounding suburbs like Kellyville and Bella Vista. Buyers often start with a unit because the deposit requirement is lower, then plan to add a house or a second unit within a few years. If the first loan pushes your DTI close to the cap, the second purchase becomes harder or impossible until you pay down debt or increase your income.

Mistake 6: Not Factoring Stamp Duty and Settlement Costs Into Your Deposit

Stamp duty is not part of the loan amount. Neither are conveyancing fees, building and pest inspections, or lender establishment costs. If you have saved a 10 per cent deposit and you are borrowing the other 90 per cent, you still need another several thousand dollars in cash to complete settlement.

For a unit purchased at the Rouse Hill median, stamp duty for an investor can sit around $20,000 to $25,000 depending on the exact price. Add conveyancing, inspections, and loan costs, and you are looking at close to $30,000 in upfront expenses that sit outside the purchase price. If you have exactly 10 per cent saved and nothing else, you cannot settle.

Lenders want to see genuine savings, and they want to see that you can cover these costs without borrowing further or relying entirely on gifted funds. When we structure an investment loan, we work backwards from settlement to make sure every cost is accounted for before you make an offer.

Mistake 7: Choosing the Lender Based on Rate Alone

The lowest advertised rate is not always the lowest total cost, and it is almost never the most flexible product. Some lenders offer discounted rates but charge higher ongoing fees, or they limit your ability to make extra repayments, or they do not allow you to port the loan to a new property if you sell and buy again within a short window.

If your plan is to build wealth through property over ten or fifteen years, you need a loan structure that supports portfolio growth, not just a low rate today. That means looking at offset account availability, redraw conditions, the ability to split the loan between fixed and variable, and how the lender treats top-ups when you want to access equity for your next deposit.

In Rouse Hill, where a lot of buyers are purchasing their first investment property, we regularly see people lock into a fixed rate with no offset and no flexibility, then realise two years later that they cannot access equity without breaking the loan and paying a cost that wipes out any rate saving they thought they had. Rate matters, but structure and features matter more if you are planning to buy again.

The new tax rules make rental yield more important than it used to be. Body corporate fees, vacancy buffers and settlement costs all need to be in your numbers before you sign. If you are buying an investment unit in Rouse Hill and you want to see what your actual borrowing capacity looks like under the current settings, call one of our team or book an appointment at a time that works for you.

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