Beginner's guide to interest rates and borrowing power

Interest rates directly control how much lenders will let you borrow.

When rates rise, your borrowing capacity shrinks because lenders assess your ability to repay based on higher monthly repayments. When rates fall, you can typically borrow more because those same repayments now stretch further. For migrants working towards home ownership in Australia, understanding this relationship helps you time your application and choose loan structures that protect your borrowing power even when rates move.

How lenders calculate what you can borrow

Lenders assess your borrowing capacity by comparing your income against all your expenses, including the proposed loan repayment calculated at an assessment rate typically two to three percentage points above the actual home loan rates you'll pay. This buffer, called the serviceability buffer, exists to confirm you can still afford repayments if rates increase. Your borrowing capacity is the loan amount where your income minus expenses minus the buffered loan repayment still leaves enough for living costs. As assessment rates climb, that maximum loan amount drops, sometimes by tens of thousands of dollars for every half percentage point increase.

Consider someone earning $90,000 annually with $600 in monthly credit commitments and typical living expenses. At an assessment rate of 7.5%, they might qualify for a loan of around $520,000. If assessment rates rise to 8%, that same borrower's capacity could drop to around $490,000 without any change to their income or expenses. The repayment on the higher loan amount at the higher rate pushes beyond what lenders consider serviceable.

Variable rates respond faster than your application timeline

Variable rates can change between the day you receive home loan pre-approval and the day you settle on a property. Pre-approval provides an indication of your borrowing capacity based on current assessment rates, but it doesn't lock in those rates. If the Reserve Bank increases the cash rate during your property search, lenders recalculate your serviceability at formal application using the new, higher assessment rate. This can reduce your approved loan amount or require you to increase your deposit to bring the loan size back within serviceable limits.

In our experience, buyers who secure pre-approval and then take several months to find a property sometimes return to discover their borrowing capacity has shifted. The property they could afford three months ago now requires an additional $20,000 to $30,000 in deposit to meet the revised lending criteria. This affects migrants particularly when you're building savings in Australian dollars while also managing commitments in your home country.

Fixed rates offer predictable repayments but not guaranteed capacity

A fixed interest rate home loan locks your repayment amount for a set period, typically one to five years, protecting you from rate increases during that time. However, lenders still assess your application using the same buffered serviceability test, meaning your borrowing capacity is calculated as if rates could rise, even if you plan to fix. The benefit of fixing comes after approval when your actual repayments remain stable regardless of what variable rates do, giving you certainty around your budget and protecting the equity you build during the fixed period.

A borrower taking a three-year fixed rate at 6.2% still has their capacity assessed at around 8.5% to 9%, depending on the lender. Once approved and settled, their actual monthly repayment stays constant even if variable rates climb to 7% during that period. This doesn't increase the amount they can initially borrow, but it does prevent repayment shock and allows them to plan their finances with confidence, which matters when you're managing currency exchange, family remittances, or planning for permanent residency applications that require financial stability.

Split loans balance certainty against flexibility

A split loan divides your total borrowing between a fixed portion and a variable portion, typically in a ratio you choose such as 50/50 or 70/30. The fixed portion gives you repayment stability, while the variable portion lets you make extra repayments or access features like an offset account, which can reduce the interest you pay over time. This structure suits borrowers who want protection from rate rises but also want the flexibility to pay down debt faster when their income allows, which is common for migrants whose earning capacity often increases as they establish themselves professionally in Australia.

Someone borrowing $500,000 might fix $350,000 at 6.1% for three years and leave $150,000 on a variable rate at 6.4%. Their fixed repayments remain constant, while extra income from bonuses, tax returns, or salary increases can go into the offset account linked to the variable portion, reducing interest without locking those funds away. If rates fall, the variable portion benefits immediately. If rates rise, the majority of their loan remains protected. Your borrowing capacity is still assessed on the full loan amount at the buffered rate, but the structure gives you options once the loan is active.

When to apply relative to rate movements

Applying when rates are stable or trending downward gives you the highest borrowing capacity, but trying to time the market perfectly often means delaying your application and missing properties. A more practical approach is to maximise your serviceability before applying by paying down credit cards, closing unused accounts, and ensuring your income documentation is current and complete. Even a small reduction in monthly commitments can offset part of the capacity loss from a rate increase, and for migrants, making sure your overseas income or rental income is properly documented can add significantly to what lenders will approve.

If you know rates are likely to rise soon, getting pre-approval before the increase locks in your capacity for the validity period, typically three to four months. You can then search for a property with confidence that your borrowing power won't erode mid-process. If rates do rise after pre-approval but before formal application, some lenders may still honour the original assessment if the increase is modest and your circumstances haven't changed, though this isn't guaranteed and varies by lender.

Offset accounts reduce interest without changing your borrowing capacity

An offset account is a transaction account linked to your loan where the balance offsets the loan principal for interest calculation purposes. If you have $20,000 in your offset and owe $400,000, you only pay interest on $380,000. The account doesn't increase how much you can initially borrow, but it reduces how much interest you pay over the life of the loan, which builds equity faster and improves your financial position for future borrowing or refinancing. For migrants, keeping your savings in an offset rather than a separate account means your emergency funds and currency buffers are still accessible while actively reducing your debt cost.

A borrower with a $450,000 variable loan at 6.3% and $30,000 in their offset account saves around $1,890 in interest in the first year compared to the same loan without an offset. Over time, this saving compounds as more of each repayment goes toward reducing the principal. The offset balance fluctuates as you deposit income and pay expenses, but even an average balance of $15,000 delivers meaningful interest savings without requiring you to lock funds into the loan itself.

Your income matters more than the rate when capacity is tight

If rising rates have reduced your borrowing capacity below what you need, increasing your income has a larger impact than waiting for rates to fall. Lenders typically allow you to include overtime, bonuses, and secondary employment income once you can demonstrate consistency, usually with three to six months of payslips. For migrants, rental income from property in your home country can also be included, though lenders apply a discount to account for currency risk and costs. Increasing your assessed income by $10,000 annually can lift your borrowing capacity by $50,000 to $60,000, far outweighing the capacity impact of a 0.25% rate reduction.

Documenting this additional income requires planning. If you've recently started a second job or begun receiving allowances, waiting another few months to apply with a stronger income position may give you access to the property price range you're targeting. This matters particularly for migrants in skilled roles where income often increases substantially in the first few years as you gain local experience and professional recognition.

Understanding how assessment rates shape your borrowing capacity lets you approach your property search with realistic expectations and prepares you to adjust your deposit or property target if rates shift during your application. The relationship between rates and borrowing power isn't something you can avoid, but you can structure your application and loan features to minimise the impact and protect your path to home ownership.

Call one of our team or book an appointment at a time that works for you to discuss how current rates affect your borrowing capacity and which loan structure suits your circumstances.

Frequently Asked Questions