This article helps Australian families work out how much they can safely borrow for an investment property, instead of simply using the bank’s maximum. It explains how lenders think about “borrowing capacity”, why that ceiling is often higher than what’s comfortable, and how to stress-test your own numbers using higher interest rates, vacancies, repairs and real-life events. It walks through the key levers you can adjust – deposit size, LVR, loan type, buffers and offsets – and how your home loan and other debts shape what’s genuinely possible. It finishes with a practical, conversation-ready framework you can take to your broker and accountant, so you can invest without putting your family under constant financial pressure.

How Much Can You Safely Borrow for an Investment Property?

A very common starting point sounds like this:

“The bank says we can borrow $X, so that must be what we should use.”

On paper, it feels efficient. In real life, it is how people end up stressed at every rate rise, arguing about money, and living without any buffer when the unexpected turns up.

The better question is not “What is the maximum we can borrow?” but “How much can we safely borrow for an investment property without wrecking our lifestyle or sleep?”

The answer sits in the gap between the bank’s view of you and your own honest view of your family, your stress levels and your long-term plan.

The Bank’s Maximum Versus Your Safe Number

Lenders look at your income, your existing debts, basic living costs, and the type of loan and property you are asking for. They also test whether you could still service the loan if interest rates were higher than they are today. From that, they calculate a maximum borrowing figure.

That number is not built to protect your holidays, your ability to help your kids, or your peace of mind. It is designed to protect the lender.

Your safe number almost always sits below the bank’s maximum. One way to picture it is to imagine the bank’s maximum sitting at the edge of a cliff. You might technically be able to stand there, but it is not a place you want to spend the next decade. Your safe figure is a few metres back from that edge, on stable ground where you can handle a bit of bad weather.

Take Stock of Your Home Base

Before you talk about a new investment loan, it helps to be honest about where you are now.

Look first at income and stability. What is your combined after-tax income each month, and how predictable is it? A long-term PAYG job for both partners feels very different to a single self-employed income that moves around. The less stable your income, the more conservative your borrowing needs to be.

Then look at existing debts. List your home loan balance and repayments, any car or personal loans, HECS or HELP, and your credit card limits, not just the current balances. All of these affect your borrowing capacity and your monthly commitments.

Finally, check your current buffers. How much do you have in savings, offsets, redraw and other liquid assets you could access quickly? If a few large bills arrived in the same month, could you handle them calmly? That answer is the foundation everything else sits on.

Setting Practical Guardrails

Rather than chasing one perfect borrowing number, it is more useful to set a few guardrails that keep you in a safe zone.

One guardrail is a real cash buffer. Before and after the purchase, it is wise to hold at least three to six months of living expenses in cash or a true offset. If your income is variable, the upper end of that range, or even more, makes sense. If the deposit and buying costs would almost wipe that out, you are pushing too hard.

Another guardrail is to work with stress-tested repayments, not just today’s rate. Whatever rate you are being quoted now, ask yourself what the repayments would look like if rates were one to two percentage points higher. Then look at the shortfall between rent and total costs at that higher rate and decide whether that feels genuinely manageable. If the thought of that scenario makes your stomach tighten, the loan is probably too large.

Vacancy and repairs are another reality to build in. It is safer to assume that there will be at least some periods without rent and some years with more maintenance than others. If the property only works on paper when you assume perfect occupancy and almost no repairs, it is not really safe.

The final guardrail is simple: the sleep test. Imagine a year that includes a rate rise, a vacancy and an annoying, expensive repair. If you picture that and can still see yourselves staying united and reasonably calm, you are probably within your safe zone. If you can already feel the arguments, your borrowing plan needs to come back a notch.

Levers That Change How Much You Can Safely Borrow

Once the guardrails are clear, you can look at the levers that actually move your safe borrowing figure.

Loan-to-value ratio, or LVR, is one of the big ones. It is simply the loan amount divided by the property value. Higher LVRs mean smaller deposits, larger loans and usually higher risk. You may also be paying lenders mortgage insurance at the higher end. Somewhere around eighty per cent LVR is often a sensible middle ground for many families. Dropping that ratio further, if you can, reduces repayments and gives you more breathing room.

Loan type is another lever. A principal and interest loan has higher repayments because you are actually paying down the debt from day one. An interest-only loan has lower initial repayments but leaves the balance unchanged during that period. Many investors like the early cashflow of interest-only, but it can also tempt people into borrowing at levels that only make sense while the lower repayment applies. A safer approach is to model the numbers at the future principal and interest repayment, even if you start with an interest-only period.

Your choice between fixed and variable rates does not change the amount you borrow, but it changes how your risk shows up. Fixed rates give certainty for a period and then drop you back into whatever the market looks like at the end. Variable rates move with the market from the start. In either case, the safest mindset is to assume that rates can rise from where they are and to be comfortable with that.

Offset accounts round out the picture. They do not change the nominal loan size, but they give you a place to hold your buffer efficiently. Cash sitting in an offset lowers the interest you pay, while still being available if life happens. A conservative structure often looks like a reasonable deposit, a properly sized loan, and a clear buffer parked in an offset rather than scattered across different accounts.

How Your Home Loan Shapes Your Investment Choices

Your own home sits right in the middle of the investment conversation, whether you like it or not.

If your home loan is large compared with your income and you already notice it in the weekly budget, that is a sign to be cautious. In that situation, an investment property with a modest purchase price, a sensible LVR and solid, boring fundamentals is more appropriate than stretching for something aggressive.

If your home debt is lower, or you have built up significant equity and the repayments feel comfortable, you do have more room to move. That does not mean you should automatically borrow as much as possible off the back of that equity. It simply means you can consider a slightly larger investment or a more growth-leaning asset, while still staying inside your guardrails.

In both cases, the question to keep asking is not “Can we technically do this?” but “Can we carry this calmly through a normal rough patch?”

Other Debts: Small Balances, Big Impact

Car loans, personal loans, buy-now-pay-later accounts and high credit card limits all eat into the same pool of capacity you want to use for investing.

They reduce what a bank is willing to lend you and increase your monthly fixed commitments. They also signal that some of your current spending is being pushed into the future.

Clearing or at least reducing these kinds of debts before taking on an investment loan can change the picture substantially. It is very hard to say, with a straight face, that you are investing for your family’s future while simultaneously carrying a lot of short-term consumer debt.

A Simple Way to Sanity-Check Your Borrowing Range

You do not need a complex model to get a first pass at what might be safe. A simple thought exercise can get you in the right ballpark before you sit with a broker.

Start by deciding what sort of monthly top-up you are genuinely comfortable with. If the rent does not cover all of the costs, how much extra could you contribute without resentment? For some families that figure might be a couple of hundred dollars a month. For others, it might be a bit more. The actual number matters less than your honesty.

Then, take a typical property in the sort of price range and suburb you are considering. Estimate a conservative rent, not the best-case number. Add in realistic running costs like rates, insurance, management fees, and strata if it applies, along with a maintenance allowance. Now layer in a loan at the sort of LVR you are considering and calculate repayments at today’s rate and at a rate two percentage points higher.

The gap between income and total costs at that higher rate is the real test. If it sits within the monthly top-up you agreed on and still allows room to keep your buffer intact, that sort of borrowing level is probably within reach. If it pushes well beyond that comfort figure, you can either look at a lower purchase price, a larger deposit, or a different strategy.

Finally, tilt the numbers a little further by assuming a short vacancy and an annoying repair in the same year. If it still feels manageable, you are in safer territory. If you immediately feel like you would be juggling credit cards, that is a sign to adjust.

Taking Your Thinking to Your Broker and Accountant

Once you have sketched out your own view, it is worth taking it to professionals and letting them sharpen it.

A good mortgage broker can walk you through the difference between the bank’s maximum and a more conservative level for your situation. They can show you how different deposit sizes and loan structures change your risk, and how your investment loan will interact with your home loan now and later. It helps to sit down with them and say plainly that you are not chasing the highest possible figure, you are aiming for a family-first, resilient arrangement.

An accountant can then help you understand the cashflow impact over the first few years, how tax settings sit around that, and what sort of buffer they would prefer to see for someone in your position. Tax advantages can be helpful, but they should never be the main reason you do a deal or a justification for stretching too far.

If both your broker and your accountant look at the same scenario and describe it as conservative and manageable for you, that is a reassuring sign.

How Summit Thinks About Safe Borrowing

From a Summit point of view, safe borrowing has a very human definition. It is not timid, but it is family-first, numbers-honest and built for the long term.

Family-first means your investment should not leave you lying awake at night or constantly snapping at each other about costs. Numbers-honest means we do not plug rosy assumptions into a spreadsheet and call it due diligence. Long-term means setting things up so you can hold an asset through normal ups and downs without being forced to sell at the worst possible time.

There are times when it can be reasonable to stretch a little, particularly if incomes are stable, buffers are real and the asset itself is strong. There are also times when the right answer is to wait, reduce other debts, or choose a smaller first step.

What we are not comfortable with is pushing anyone to the bank’s absolute maximum, building strategies that only survive in perfect conditions, or ignoring the strain on marriages and mental health because “the numbers work”.

Safe borrowing is not about being scared of debt. It is about being deliberate with it.

Bringing It All Together

“How much can we safely borrow for an investment property?” is not something a bank calculator can answer for you. It sits at the intersection of your current reality, your values, your resilience and some simple but firm guardrails.

In practice, it means using the bank’s maximum as a reference point, not a target; keeping genuine cash and offset buffers; stress-testing repayments at higher rates with vacancies and repairs built in; being clear on how much monthly support you can comfortably give the property; and working with a broker and accountant who understand that you are playing a long game.

When you approach borrowing this way, the loan stops being a bet on everything going right. It becomes a tool you are using, with eyes open, to build something that actually serves your family over time.

‍