How to Weigh Property Values Against Interest Rate Changes

Property prices move slowly, interest rates move fast, and your investment loan sits squarely in the middle.

Investors often focus on whichever number is changing most. When rates jump, the panic is whether repayments are sustainable. When property values climb, the temptation is to borrow more. Both are important, but neither tells the full story on its own. Your borrowing capacity, the loan structure you choose, and the income your property generates all matter more than either figure in isolation.

How Interest Rates Affect What You Can Borrow

Investor borrowing capacity is calculated using a serviceability buffer of at least 3.0 percentage points above the loan product rate. If you're looking at a variable rate investment loan currently sitting around 6.5 per cent, your lender assesses serviceability at 9.5 per cent or higher. That buffer has been in place since late 2021 and shapes how much you can borrow regardless of whether you choose a fixed or variable rate investment loan.

Consider a buyer looking to purchase a rental property who earns $120,000 a year with no other debts. At current variable rates, the lender tests whether they can service repayments at around 9.5 per cent. That might cap their borrowing at roughly $550,000, even though the actual repayments at 6.5 per cent are far lower. If rates fall by one percentage point, the buffer still applies, so borrowing capacity might only increase by $50,000 to $60,000. The buffer dampens how much lower rates translate into higher loan amounts.

Debt-to-income limits also play a role. From February this year, lenders can only write up to 20 per cent of new investment loans to borrowers with total debt more than six times their income. If your gross income is $120,000, total borrowing above $720,000 falls into that restricted bucket. Most investors won't hit that ceiling, but if you're leveraging equity from an existing property or holding other loans, it can cap how much further you can stretch.

Property Values and Equity Release

Property growth doesn't directly increase your borrowing capacity, but it does increase your equity, and equity is what lets you borrow again without selling. If you bought a property for $500,000 with a $400,000 loan and it's now worth $600,000, your equity has grown from $100,000 to $200,000. Lenders will typically let you borrow against up to 80 per cent of that new value without paying Lenders Mortgage Insurance, which means you could access roughly $80,000 in equity for a deposit on a second property.

In our experience, investors who rely on property growth to fund their next purchase often underestimate how much cash they still need at settlement. Equity can cover the deposit, but stamp duty, legal fees, and lender costs still need to come from savings or further borrowing. If you're pulling equity from a property in regional Victoria where values have risen steadily over the past few years, you might have the deposit sorted but still need $15,000 to $20,000 in cash to settle.

The loan-to-value ratio matters more than the dollar figure. A property that's grown in value gives you more equity to leverage, but it doesn't change your income, and income is what determines how much debt you can service. You can own a $1 million property with $500,000 in equity and still be unable to borrow another dollar if your income won't support the repayments.

What Happens When Property Values Drop

Falling property values don't trigger margin calls or forced sales on residential investment loans, but they do limit your options. If the property you bought for $600,000 drops to $550,000 and you owe $480,000, your equity shrinks from $120,000 to $70,000. You can keep making repayments without any issue, but if you wanted to refinance or access equity, most lenders would treat your loan-to-value ratio as 87 per cent, which puts you above the 80 per cent threshold and means you'd either pay LMI or be unable to refinance at all.

This becomes relevant when fixed rate periods end. If your fixed rate is expiring and you want to move lenders for a lower rate, but your property value has dropped and you're now above 80 per cent LVR, you might be stuck with your current lender's standard variable rate rather than securing a discounted rate elsewhere. The loan amount hasn't changed, but the property value has, and that's what determines whether you can move.

Rental income doesn't change with property values either. A property that's dropped $50,000 in value still generates the same weekly rent. For investors holding long term, the income and the loan structure matter more than short-term valuation shifts.

Interest-Only Versus Principal and Interest Repayments

Interest-only investment loans keep repayments lower during the interest-only period, which helps with cash flow, particularly if the rent doesn't fully cover the loan repayment. Most lenders offer interest-only periods of up to five years on investment loans, after which the loan reverts to principal and interest unless you negotiate an extension.

From a tax perspective, all the interest on an investment loan used to acquire or hold a rental property is deductible, whether the loan is interest-only or principal and interest. Paying down principal doesn't increase your tax deduction. If you're negatively geared and relying on the tax benefit to make the numbers work, an interest-only loan maximises that deduction by keeping the loan balance higher for longer.

However, interest-only loans generally attract slightly higher interest rates than principal and interest loans, and under the prudential framework, they're treated as higher risk, which flows through to pricing. If you're planning to hold the property long term and build equity through capital growth rather than loan repayments, interest-only can make sense. If your goal is to pay the loan down and reduce debt, principal and interest is the better fit. Neither structure changes what you can borrow, but both affect your cash flow and tax position.

Fixed or Variable: Matching Loan Features to Your Strategy

Fixed rate investment loans lock in your repayment for a set period, usually one to five years, which makes budgeting easier and protects you if variable rates rise. The downside is reduced flexibility. Most fixed loans limit extra repayments to $10,000 or $20,000 a year, and if you want to break the loan early to sell or refinance, break costs can be substantial if rates have fallen since you fixed.

Variable rate investment loans give you full flexibility to make extra repayments, redraw, or pay the loan out at any time without penalty. Offset accounts are generally only available on variable loans, and for investors, an offset can be useful if you're accumulating cash for your next purchase while still reducing the interest you pay. Not all lenders offer offset accounts on investment loans, and those that do may charge a higher rate or annual fee.

In a falling rate environment, variable loans benefit immediately. In a rising rate environment, fixed loans provide certainty. If property values are climbing and you're planning to leverage equity within a couple of years, a variable loan gives you the flexibility to refinance or restructure without penalty. If you're holding long term and want predictable repayments, fixing part or all of the loan can make sense. A split loan, where part is fixed and part is variable, is a middle option that some investors use to balance certainty with flexibility. You can read more about refinancing if your current loan structure no longer suits your circumstances.

Rental Income and Serviceability Calculations

Lenders assess rental income at a discount, typically using 80 per cent of the rental income to account for vacancy periods, maintenance, and holding costs. If the property generates $500 a week in rent, the lender will treat it as $400 a week when calculating your borrowing capacity. Some lenders apply a lower discount, around 70 per cent, depending on their policy and the property type.

If you're buying a property where the rent is $450 a week and the loan repayment is $650 a week, you're negatively geared by $200 a week, or roughly $10,400 a year. That shortfall needs to be covered by your salary, and the lender will factor that into their serviceability assessment. The tax deduction you receive for the loss reduces the after-tax cost, but it doesn't change the cash flow requirement. You still need to fund the gap each week, even if you get some of it back at tax time.

Rental income doesn't increase your borrowing capacity dollar for dollar. Because lenders discount it and because most investment properties are negatively geared, adding an investment property to your portfolio typically reduces how much you can borrow for your next purchase, even though you've added an income-producing asset. Your overall debt has increased more than your income, and that's what the lender sees.

How to Position Yourself for the Next Purchase

If your goal is to build a portfolio, structuring your first investment loan correctly makes the second purchase easier. Investors who max out their borrowing capacity on the first property often find they can't borrow again until their income increases or they pay down debt. Leaving some serviceability buffer gives you room to add another property without waiting years for equity to build or for rates to fall.

Keeping your loan structure flexible also helps. If you've locked everything into a fixed rate with no offset and no ability to make extra repayments, you can't adjust your position if your circumstances change. A variable loan or a split loan with an offset account gives you more options when it's time to pull equity or restructure. We regularly see investors who want to buy a second property but are stuck because their loan structure doesn't allow them to access equity or refinance without penalty.

You can check your current position with a loan health check to see whether your loan structure still matches your goals, particularly if your circumstances or the market have shifted since you first borrowed.

Property values and interest rates both matter, but your loan structure, your income, and your ability to hold the property through different conditions matter more. Get those right, and you can build wealth regardless of whether rates rise or fall in any given year.

Call one of our team or book an appointment at a time that works for you.

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