Investment Loans: Avoid These 3 Rate Structure Mistakes

Most investors in Marrickville choose a variable rate because it feels like the default.

That's understandable, but it's worth asking whether a fixed rate, or a combination of both, might give you more control over your cash flow and more room to move when tax rules shift.

The right rate structure for an investment property loan depends on what you need the loan to do over the next few years, not just what the advertised rate is today. A variable rate gives you flexibility to make extra repayments and offset rental income against the balance. A fixed rate locks in your borrowing cost and makes it easier to forecast your holding costs. A split loan tries to do both.

Each approach has trade-offs, and the structure you choose now will shape how much flexibility you have when interest rates move, when rental income changes, or when new rules around negative gearing and capital gains come into effect from mid-2027.

Variable Rates Give You Room to Adjust as Rental Income Comes In

A variable rate loan lets you make extra repayments, redraw funds if the lender allows it, and link an offset account to reduce the interest charged on the outstanding balance.

For an investment property, that means rental income can sit in an offset account and reduce the amount of interest you pay each month without affecting your ability to claim the full loan interest as a deduction. The loan balance stays the same, so your deductible interest doesn't reduce, but the actual cost to you does.

Variable rates move with the Reserve Bank cash rate and with competition between lenders. That can work in your favour when rates fall, but it also means your repayments can rise quickly if the cash rate increases. Serviceability buffers mean you'll have been assessed at a rate around three percentage points above the product rate, but that doesn't make the higher repayment comfortable if rental income stays flat.

If you're holding a newer property in Marrickville with solid rental demand from sharers and young professionals near the train line, a variable rate with an offset account can give you the flexibility to manage short vacancy periods without needing to dip into savings elsewhere.

Fixed Rates Lock In Your Borrowing Cost but Limit Your Options

A fixed rate gives you certainty over what your repayments will be for a set period, usually between one and five years.

That certainty is valuable if you're buying a property where the rental yield is tight and you need to know exactly what your monthly holding cost will be, especially if you're managing multiple properties or planning to add another investment before the fixed term ends.

The limitation is that most fixed rate investment loans don't allow extra repayments beyond a small annual cap, typically around $10,000 to $20,000 depending on the lender. You also can't link an offset account to a fixed rate portion, so any rental income sitting in your bank account won't reduce the interest charged.

If you need to exit the loan early, either to sell the property or to refinance to a better rate, you'll likely face break costs. Those costs reflect the difference between the fixed rate you're paying and the rate the lender can now earn by lending that money elsewhere. In a falling rate environment, break costs can be significant.

For properties acquired before 7:30pm AEST on 12 May 2026, rental losses can still be offset against other income under the existing negative gearing rules. For properties acquired after that time, rental losses from non-new builds will be quarantined from 1 July 2027 and can only offset other residential rental income or future capital gains. If you're planning to hold a property through that transition and your cash flow is already tight, locking in a rate for three to five years removes one variable from the equation.

A Split Loan Tries to Balance Certainty and Flexibility

A split loan divides your borrowing between a fixed portion and a variable portion.

You might fix 50 per cent of the loan to lock in half your repayment, and leave the other 50 per cent variable so you can make extra repayments, use an offset account, and take advantage of any future rate cuts without paying break costs.

The split doesn't have to be even. Some investors fix a smaller portion, say 30 per cent, just to create a floor under their repayment while keeping most of the loan flexible. Others fix a larger portion if they want more predictable holding costs and only need a small amount of flexibility for managing rental income.

Split loans do add a layer of administration. You'll have two loan accounts, sometimes two sets of fees, and you'll need to decide how to allocate repayments and any surplus rental income between them. Some lenders handle this smoothly, others make it harder than it needs to be.

Consider an investor buying a two-bedroom apartment in the Marrickville Station precinct. The rental income covers most of the interest, but not all of it. They fix 60 per cent of the loan for three years to lock in that portion of the repayment, and leave 40 per cent variable with an offset account. Rental income flows into the offset, reducing interest on the variable portion. If interest rates fall, the variable portion benefits immediately. If rates rise, the fixed portion shields them from the full impact.

Interest-Only Repayments Reduce Your Monthly Outlay but Increase Your Long-Term Cost

Most investment property finance is structured as interest-only for the first few years, then switches to principal and interest.

Interest-only repayments mean you're only paying the interest charged each month. The loan balance doesn't reduce, so your repayment is lower than it would be on a principal and interest loan. That can improve your cash flow in the early years, especially if you're holding multiple properties or building a portfolio.

The downside is that when the interest-only period ends, your repayment increases because you then start paying down the principal as well. If rental income hasn't increased in line with that jump, you'll need to cover the gap from other income or savings.

Interest-only also means you're not reducing the loan balance, so if property values don't increase as expected, you won't build equity through repayments. You'll build it only through capital growth.

For properties acquired after 12 May 2026 that aren't eligible new builds, rental losses will be quarantined from 1 July 2027. That means the tax benefit of negative gearing disappears, and holding costs become more important. If your strategy relies on offsetting rental losses against salary, you'll need to adjust your approach for any property acquired after that date.

Interest-only can still make sense if your goal is to minimise cash outflow while you build equity elsewhere, or if you're planning to sell before the interest-only period ends. It's less suitable if you're planning to hold for the long term and want to reduce debt over time.

How Lenders Assess Borrowing Capacity for Investment Loans Under Current DTI Rules

Lenders assess investment loan applications differently to owner-occupied loans.

They'll include a portion of the expected rental income, usually 80 per cent, to allow for vacancy and management costs. They'll also add the full loan repayment to your existing commitments when calculating serviceability.

From 1 February 2026, lenders must apply a debt-to-income cap. No more than 20 per cent of new investor loans can be made to borrowers with total debt of six times their gross income or more. That cap applies across the lender's entire investor loan portfolio, so some lenders are stricter than others depending on how close they are to the limit.

If you already have a home loan and you're borrowing to buy an investment property, the combined debt needs to fit within the lender's serviceability buffer and, depending on your income, may be affected by the DTI cap.

A practical option is to refinance your existing home loan at the same time as applying for the investment loan, so both loans are assessed together and you can access any equity in your home to fund the deposit or cover upfront costs like stamp duty and Lenders Mortgage Insurance.

You can get a clearer sense of how much you might borrow using a borrowing capacity assessment before you start looking at properties. That removes some of the uncertainty and lets you focus on properties that fit within your budget.

Switching Between Fixed and Variable After Settlement

Most lenders let you switch from variable to fixed at any time, though you'll need to reapply and the rate you're offered will be the current fixed rate at that time, not the rate available when you first settled.

Switching from fixed to variable before the fixed term ends will usually trigger break costs, unless interest rates have risen significantly since you fixed and the lender's cost to replace your loan is lower than the rate you're paying.

If you're on a split loan and you want to change the proportions, most lenders will let you do that, but again it's treated as a partial break and refinance, so costs can apply.

Some investors start with a variable rate, watch where interest rates are heading over the first six to twelve months, then fix a portion once they have a clearer view. Others fix at settlement and plan to refinance the whole loan when the fixed term ends, either to a new fixed rate or back to variable depending on what's happening with rates at that time.

If you're holding a property in Marrickville with strong rental demand and you're confident you can cover any rate rise, staying variable gives you more options. If your cash flow is tighter and you'd rather remove the uncertainty, fixing part or all of the loan makes sense even if the fixed rate is slightly higher than the current variable rate.

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