The Easiest Way to Keep Investment Cash Flow Positive

Rental income covers the mortgage until it doesn't.

In Randwick, where the vacancy rate sits low but tenants still move on, a fortnight without rent can push an investment property from neutral cash flow into a borrowing cycle that takes months to correct. The goal is to structure your loan and hold enough buffer that you can manage a gap in rental income, a plumbing repair, or a body corporate special levy without relying on your credit card or redrawing against equity you've worked to build.

Setting Up the Loan to Match Rental Income Cycles

Rental income arrives fortnightly or monthly, and the mortgage debit should line up with that cycle. Most lenders let you choose your repayment frequency when you settle the loan. If your tenant pays fortnightly, set the mortgage debit to fortnightly on the same week. If they pay monthly, align your interest-only payment to follow a few days later. The goal is to avoid a situation where the mortgage debits on the first of the month but the rent doesn't arrive until the tenth, leaving you to cover the shortfall from your offset or another account.

Consider a buyer who purchased a two-bedroom apartment in Randwick with an investment loan at 80 per cent LVR. The property rented for $750 per week, paid fortnightly, and the interest-only repayment was roughly $1,400 per fortnight. The buyer set the loan repayment to debit three days after the rent hit the account, creating a rhythm where income and outgoing matched without manual intervention. When the tenant gave notice and the property sat vacant for three weeks, the buyer had already set aside a buffer equal to two months of repayments in the loan offset account, so the mortgage continued to debit without touching other savings.

Interest-Only Loans and When They Suit Cash Flow

An interest-only loan reduces the monthly outgoing to just the interest portion, which can keep an investment property cash flow neutral or slightly positive where a principal-and-interest loan would create a monthly shortfall. The downside is that you're not reducing the debt, so the loan balance stays flat and you don't build equity through repayment, only through capital growth or additional contributions.

Interest-only periods on investment loan products typically run for one to five years, after which the loan reverts to principal and interest unless you apply to extend. Lenders assess the extension request based on your income, the property's current value, and your overall serviceability at that time. Extending isn't automatic. If the property value has dropped or your income has changed, the lender may decline the extension or require a switch to principal and interest.

In our experience, buyers who plan to hold the property long-term and build wealth through capital growth often start with interest-only to maximise cash flow in the first few years, then switch to principal and interest once their income increases or they refinance to release equity. Buyers who want to reduce the loan balance quickly, or who are close to retirement and want the debt cleared, tend to choose principal and interest from the start, even if it means the property runs at a small monthly loss.

Offset Accounts and Redraw: Which One Protects Cash Flow

An offset account is a transaction account linked to the investment loan. Every dollar in the offset reduces the interest charged on the loan balance without actually paying down the principal. If you have a loan of $600,000 and $20,000 sitting in the offset, you're charged interest on $580,000. The cash in the offset stays accessible at all times, and you can deposit rental income, withdraw for repairs, or move funds between accounts without affecting the loan structure.

Redraw works differently. When you make extra repayments above the minimum, those funds sit against the loan balance and reduce the interest. You can apply to redraw those funds later, but the lender controls the approval and processing time. Some lenders charge a fee for each redraw, and some lenders have reduced or removed redraw availability during periods of financial stress, as seen during the pandemic. For an investment property, where you may need to access funds quickly to cover a vacancy or urgent repair, an offset account gives you more control.

Not all investment loan products include an offset account, and some lenders charge a higher interest rate for loans with offset. The rate difference is typically between 0.10 and 0.30 percentage points per year. You need to weigh the cost of the higher rate against the value of having instant access to your cash buffer. For a loan of $500,000, a 0.20 percentage point increase costs roughly $1,000 per year. If that buys you the ability to cover a three-week vacancy or an emergency repair without waiting for redraw approval, it's often worth the cost.

Building a Cash Buffer Without Overcapitalising

The rule that works in Randwick's rental market is to hold a buffer equal to two to three months of total property costs in the offset account or a separate savings account linked to the investment. Total property costs include the mortgage repayment, strata levies, council rates, landlord insurance, and an allowance for minor repairs. For a property with a $1,400 fortnightly mortgage, $1,200 quarterly strata, $400 quarterly council rates, and $800 annual insurance, the monthly cost is roughly $3,500. A three-month buffer would be around $10,500.

You don't need to have that full amount sitting in the offset from day one. Many buyers start with one month's buffer and build it over the first year by directing surplus rent into the offset rather than spending it. If the property generates $3,000 per month in rent and costs $3,200 per month to hold, the monthly shortfall is $200. You cover that from your salary, and any bonus rental income or periods where the property sits vacant less than expected go into building the buffer.

Vacancy and Tenant Turnover: The Cost Most Buyers Underestimate

Randwick's rental vacancy rate has hovered low for years, driven by demand from students at the University of New South Wales, medical professionals working at the Prince of Wales Hospital, and young professionals commuting to the city. Low vacancy doesn't mean zero vacancy. Tenants finish contracts, move interstate, or buy their own home. The gap between one tenant moving out and the next moving in typically runs two to four weeks, depending on the time of year and the condition of the property.

During that gap, you're still covering the mortgage, strata, insurance, and any costs to prepare the property for the next tenant, which might include a professional clean, minor repairs, or repainting if the lease was long. If the property rents for $750 per week and sits vacant for three weeks, you've lost $2,250 in income. If the mortgage and other costs for those three weeks total $2,100, the total cash impact is $4,350. Without a buffer, that amount comes out of your offset or savings, and if those accounts are already drawn down, you're using a credit card or delaying other financial goals.

Some buyers try to avoid vacancy by keeping the rent below market or accepting tenants with weaker references. Both approaches create different problems. Below-market rent costs you thousands per year in lost income, and difficult tenants can result in tribunal costs, property damage, or longer vacancy periods when they eventually leave. The better approach is to price the property at market rent, maintain it well, and build a cash buffer that lets you manage a standard vacancy period without financial stress.

How Borrowing Capacity Affects Portfolio Growth

Every dollar of rental income increases your borrowing capacity for the next investment property, and every dollar of rental shortfall reduces it. Lenders apply a shading rate to rental income, typically between 75 and 80 per cent, meaning they only count $750 to $800 of every $1,000 in rent when calculating your serviceability. They also add the full interest cost of the existing investment loan to your liabilities, along with an assumed principal-and-interest repayment even if you're on interest-only, and they assess your capacity to service all loans at the product rate plus the 3.0 percentage point buffer.

If your first investment property runs at a monthly cash flow loss of $400, that loss reduces your borrowing capacity for a second property by roughly $80,000 to $100,000, depending on your income and other debts. If the property runs cash flow neutral or slightly positive, your borrowing capacity is preserved, and you can move toward a second acquisition sooner. This is one reason buyers in Randwick, where rental yields tend to sit below 4 per cent due to higher property values, often choose interest-only loans and structure the deposit to avoid Lenders Mortgage Insurance, which would otherwise add to the upfront cost and reduce the cash buffer available at settlement.

Checking your borrowing capacity before committing to a second investment property lets you see whether the rental income from your existing portfolio is carrying its weight or dragging on your serviceability. If the numbers don't stack up yet, you can wait for rents to increase, pay down other debts, or consider refinancing the first property to improve the loan structure before adding a second.

Tax Deductions and How They Affect Monthly Cash Flow

Interest on an investment loan, strata fees, council rates, landlord insurance, property management fees, repairs and depreciation are all claimable expenses against the rental income when you lodge your tax return. If your total claimable expenses for the year exceed the rental income, the loss can be deducted against your salary or other income, reducing your overall tax liability. That refund doesn't arrive until you lodge your return, which could be up to twelve months after you incurred the expense.

Some buyers adjust their PAYG withholding through the ATO once the investment property settles, which increases their take-home pay each fortnight and smooths out the cash flow impact rather than waiting for a lump sum refund at tax time. You lodge a withholding variation through the ATO online, and the ATO assesses your expected deductions and issues a new withholding schedule to your employer. The process takes a few weeks, and you need to update it each year if your circumstances change.

From the 2027-28 income year, established properties acquired after 12 May 2026 are subject to different negative gearing rules, where losses can only be offset against other residential property income rather than salary. If you're considering a property that will run at a loss, it's worth speaking to an accountant about how the new rules will affect your after-tax cash flow and whether the property still fits your longer-term wealth plan.

Call one of our team or book an appointment at a time that works for you. We'll look at your current loan structure, your rental income, and your plans for the next property, and help you set up a loan and offset arrangement that keeps your cash flow steady without relying on credit or eating into savings you've set aside for other goals.

Frequently Asked Questions