Most people are surprised by how much less they can borrow for an investment property than they expect. The reason is that lenders do not assess an investment loan the way you would work it out yourself.
Lenders assess you at a higher rate than you will pay
Every lender applies an assessment buffer. They test whether you could still afford the repayments if rates rose by a set margin above the actual rate, and they also apply a floor rate, so even a very low advertised rate gets assessed at a much higher one.
This is why the repayment you see on a calculator and the repayment the lender assesses are different numbers. Your borrowing power is calculated on the second one.
It applies to your existing home loan too, not just the new one. The lender reassesses your current mortgage at the buffered rate as well, which is why taking on a second property reduces your capacity more than the new loan alone would suggest.
Only part of your rental income counts
You might expect $600 a week in rent to count as $600 a week of income. It will not.
Lenders shade rental income, commonly counting around 80% of it, to allow for vacancy periods, management fees, rates, insurance and maintenance. Some go further for certain property types.
The shading is not uniform. A standard house or apartment in an area with strong rental demand is treated more generously than a serviced apartment, a studio under a certain size, a rural property, or something in a postcode the lender considers exposed. Two lenders can look at the same property and reach different conclusions.
Your existing debts count for more than the repayments
Credit cards are assessed on the limit, not the balance. A card with a $20,000 limit and nothing owing on it still reduces your borrowing power, because the lender assumes you could draw the full amount tomorrow.
The same logic applies to other lines of credit and buy now pay later facilities. Closing or reducing facilities you do not use is one of the few things that can lift your capacity quickly, and it is worth doing well before you apply rather than during the assessment.
Living expenses matter too. Lenders use a benchmark figure but will use your actual spending if it is higher, and they verify it against your statements. How living expenses affect borrowing power.
Interest only changes the picture, in both directions
Interest only lowers your actual repayment during the interest only period, which improves cash flow. Investors often choose it for that reason.
It does not always improve your borrowing power though. Many lenders assess an interest only loan on the principal and interest repayment over the remaining term after the interest only period ends, which is a shorter term and therefore a higher assessed repayment. The result can be that interest only helps your monthly cash flow and reduces what you can borrow at the same time.
The 2026 tax changes affect serviceability, not just tax
This is the part that is easy to miss, because it looks like an accountant’s issue rather than a lending one.
Under the 2026 reforms, an established property bought after 12 May 2026 loses the ability to offset rental losses against your salary from 1 July 2027. For a negatively geared investment, that tax refund was part of how the shortfall got funded. Without it, the same property costs you more in after-tax cash flow each year.
Whether and how individual lenders reflect that in their assessment models is still working through the market. Either way, the underlying point stands: a property that relied on the tax deduction to be affordable is a tighter proposition than it was. What changed in 2026.
Lenders differ, and the difference is large
Borrowing power is not one number. It is a different number at every lender.
They use different floor rates, shade rental income differently, treat existing debts differently, and apply different policies to particular property types, employment types and income sources. The gap between the most and least generous lender on the same application can be substantial.
That is the practical argument for comparing across a panel rather than asking one lender and accepting the answer. It is also why a declined application at one lender does not mean the deal is not doable. Why applications get rejected.
What you can actually change
- Reduce or close unused credit card limits and other credit facilities
- Clear personal loans and car finance where you can
- Tidy up discretionary spending for a few months before applying, since statements get reviewed
- Lower your LVR, which widens which lenders will consider you and can avoid lenders mortgage insurance
- Choose a property type that lenders assess favourably rather than one they shade heavily
You can work out your LVR here, and check the rental yield on a property you are considering.
Common questions
Why can I borrow less for an investment property than for my home?
Lenders count only part of your expected rental income, usually around 80%, and they reassess your existing home loan at a buffered rate at the same time. Both work against you, so the capacity for a second property is lower than the first.
Does a credit card I never use affect my borrowing power?
Yes. Lenders assess credit cards on the limit rather than the balance, because you could draw the full amount at any time. Reducing or closing unused limits is one of the quickest ways to lift your capacity.
Will interest only let me borrow more?
Often the opposite. It lowers your actual repayment, but many lenders assess an interest only loan on principal and interest over the shorter remaining term, which raises the assessed repayment. It helps cash flow more reliably than it helps borrowing power.
Why did one lender say no when another said yes?
Because they use different floor rates, shade rental income differently, and apply different policies to property types, employment types and income sources. A decline at one lender says nothing definitive about whether the deal can be done elsewhere.
New to property investing? Start with our guide on how to buy an investment property in Australia.