Investment Property Loans: How to Check Cash Flow Before You Buy
The decision to buy an investment property is typically made on two numbers: the purchase price and the rent. The purchase price determines the loan. The rent seems to cover the repayment. The deal looks workable.
What actually determines whether the deal works is the gap between what the rent promises and what the property delivers after every real cost has been deducted. That gap: the true net cash position is almost always smaller than the initial calculation suggests, and for some properties, it runs in the wrong direction entirely. Running the investment property cash flow calculation properly before you commit is not optional. It is the decision. The following example assumes a $650,000 investment property, with a $520,000 loan representing an 80% LVR, at an illustrative interest rate of 6.5% over 30 years.
The Full Calculation: Run It on Any Property You're Considering
| Cash Flow Item | Annual Amount |
|---|---|
| Gross rental income ($690 × 52) | $35,880 |
| Property management (9% assumption) | −$3,229 |
| Council rates | −$1,500 |
| Water rates | −$900 |
| Landlord insurance | −$1,400 |
| Maintenance allowance* | −$6,500 |
| Vacancy allowance (2 weeks) | −$1,380 |
| Letting/reletting allowance* | −$1,035 |
| Net income before mortgage | $19,936 |
| P&I repayments: $520,000 at 6.5%, 30 years | −$39,441 |
| Illustrative cash position before tax | −$19,505/year |
That is approximately $375 per week out of pocket before tax under these assumptions. Based on the assumed $650,000 property price, the resulting investment property net yield before finance is approximately 3.1%.
This is an illustrative rental property cash flow calculation. Actual management fees, vacancy, insurance, rates, and investment property maintenance costs vary by property and location. Land tax, strata/body corporate fees, depreciation, and capital expenditure may also apply.
What This Calculation Actually Tells You
Based on an assumed purchase price of $650,000, the property has a gross yield of approximately 5.5% and still runs at a negative cash-flow position under the assumptions above. That is not a disaster; it is a known, manageable cost attached to an asset that, in the right market, compounds through capital growth over a 10-year hold. The question is whether the investor going in understood that cost or assumed the gross rent would cover everything.
The calculation changes materially at several pressure points. “First is vacancy." This model assumes two weeks without rent each year, but actual vacancy depends on the suburb, property, and tenant demand. At $690 per week, every additional vacant week reduces rental income by another $690. “Second is investment property maintenance." The 1% allowance used above is an illustrative planning assumption, not an industry rule. Actual costs depend on the property’s age, condition, features, and upcoming repairs, so investors should model the property itself rather than rely on a fixed percentage.
Third is the interest-rate assumption. The model above uses 6.5% purely as an illustrative investment property loan rate. Actual rates vary by lender, LVR, repayment type, borrower profile, and loan features.
Stress-test the cash flow at a higher rate, not just today’s rate. For example, Moneysmart suggests exploring what would happen if interest rates increased by 2%. The aim is not to predict rates, but to understand whether the property remains manageable if repayments rise.
The Loan Structure Question That Most Investors Skip
The cash flow model is one half of the investment property finance decision. The other half is loan structure – and the two interact in ways that most borrowers don't model before applying.
Some investors consider interest-only repayments to preserve cash flow while directing additional funds toward non-deductible home debt. However, interest-only is not automatically the better structure. Tax deductibility depends on how borrowed funds are used. From 1 July 2027, the legislated negative-gearing changes affect certain established residential properties acquired from 12 May 2026, while eligible new builds and grandfathered properties are treated differently. Loan structure should therefore be considered alongside the investor’s cash flow, debt position, and professional tax advice.
A mortgage broker in Australia that investors work with can compare an investment property loan across lenders based on rates, repayment type, loan features, and credit policy, not simply the lowest advertised rate. Tax-specific structuring should be confirmed separately with a qualified tax adviser.
Where KM Financial Service Fits In
Kris Menon and the KM Financial Service team help investors compare cash flow, repayments, and suitable loan structures before applying for finance.
With 20 years of lending and real estate experience, KM Financial Service works with clients across Australia, comparing investment loan options across Australian banks and lenders based on each borrower’s financial position and broader property investment strategy in Australia.
KM Financial Service has also received 400+ Google Reviews and 400+ Rate My Agent reviews, reflecting feedback from clients across its lending services.
Book your free session review at kmfinancialservice.com.au. Or contact KM Financial Service on 0402879531. You can also follow KM on social media: Instagram, Facebook, and LinkedIn.
Frequently Asked Questions
Q: What gross yield do I need for an investment property to be positively geared?
Answer: There is no single required yield. Positive cash flow depends on the loan size, interest rate, rent, vacancy, management fees, rates, insurance, and maintenance costs.
Q: Is interest-only always better for investment property loans?
Answer: No. An interest-only loan can improve short-term cash flow, but the principal does not reduce, and repayments generally rise when the IO period ends. Whether it suits an investor depends on their loan structure, goals, and financial position.
Q: How much should I budget for maintenance on an investment property per year?
Answer: There is no universal percentage. Maintenance costs vary with the property's age, condition, and features, so use a property-specific allowance and keep a separate buffer for larger repairs.
