The costs of owning a property do not arrive together

A mortgage is usually the largest and most recognisable item in a property budget.

It follows a schedule. It leaves the same account. In many households, the payment happens automatically. When interest rates change or a fixed term ends, the repayment receives attention again.

The rest of the property budget is rarely as orderly.

Council and water rates arrive periodically. Insurance renews annually. Strata levies follow their own timetable. A plumber sends an invoice by email. A receipt for an appliance ends up in a drawer. Pest control, gardening, repairs and routine maintenance appear throughout the year.

Each expense may be understood when it arrives. What is harder to see is what they mean together.

The largest expense is often the easiest one to find

Interest rates receive attention for good reason. A change can alter repayments and the money available for everything else.

The mortgage is also usually the easiest property expense to identify. It appears regularly on a bank statement and is commonly paid by direct debit.

For households entering the Sydney market, that visible commitment can consume a particularly large share of income. Cotality estimated that, in September 2025, a median-income household taking out a new mortgage on a median-valued Sydney house would need 68.1% of its pre-tax income to service the loan. The corresponding estimate for a Sydney unit was 38.7%.

These are affordability measures for a new purchase, not the amount every Sydney owner pays. The calculation assumed a 20% deposit, a 30-year loan and the average new owner-occupier lending rate available at the time, which Cotality put at 5.75%. They are the latest figures in Cotality's affordability series and describe conditions as at September 2025.

The figures still illustrate an important point. When much of the household income is already committed to a mortgage, the rates notice, insurance renewal or unexpected repair does not arrive into an empty budget.

The pressure looks different across Australia

Cotality's research also shows why a single national description cannot explain every owner's experience.

In September 2025, the estimated share of income required to service a new mortgage on a median-valued house was 53.6% in Adelaide, 52.7% in Brisbane, 45.9% in Melbourne and 44.2% in Perth. Outside the capital cities, the house estimates ranged from 51.4% in regional New South Wales to 23.5% in the regional Northern Territory.

Property type matters too. A median-valued unit required an estimated 38.7% of income in Sydney and 41.0% in regional New South Wales. In regional Queensland, the house and unit estimates were unusually close at 46.9% and 45.1%.

Regional does not always mean inexpensive. A unit does not always create the same affordability advantage. The household budget depends on the local market, the property type and the circumstances of the owner.

Broad statistics provide context, but cannot describe an individual property budget.

The expenses around the mortgage create the surprises

The mortgage is only one line.

Other property expenses can include:

• council and water rates
• building, contents or landlord insurance
• strata or owners corporation levies
• repairs and preventative maintenance
• pest inspections and treatments
• gardening, appliances and exterior upkeep
• trade invoices, reports and certificates
• improvements and renovation work

Some costs can be anticipated. Others emerge with little warning. They may be paid from different accounts and supported by records scattered between inboxes, filing systems and paper receipts.

This fragmentation can make a modest expense feel more alarming than its amount alone would suggest. The owner is not only deciding how to pay it. They may also be trying to understand how it fits beside everything else the property has already cost that year.

What does maintenance usually cost?

There is no percentage that predicts the maintenance needs of every property.

Australian housing research does, however, offer a useful reference point. Reserve Bank research published in 2014, drawing on landlord tax data, estimated repairs and maintenance at approximately 0.3% of property value each year. A 2025 Australian Housing and Urban Research Institute model continued to use the same 0.3% assumption when estimating the ongoing cost of home ownership.

At that rate, the annual allowance would be approximately A$1,500 for a A$500,000 property, A$3,000 for a A$1 million property and A$4,500 for a A$1.5 million property.

That research benchmark is broadly consistent with Allianz's 2025 survey, in which Australian homeowners estimated their average annual maintenance spending at A$3,400. The findings use different methods and should not be treated as a direct comparison, but they sit in a similar range.

The familiar 1% suggestion is better understood as a conservative reserve rule than a measured Australian average. On a A$1.5 million property, it implies A$15,000 a year. That may suit some older or complex homes, but not every property.

Age, size, condition, materials, climate, exposure and previous maintenance are usually more relevant than one percentage alone.

Market value and insured value answer different questions

Property market value includes both the building and the land.

This matters in markets such as Sydney, where land can account for a large part of the purchase price. A rise in land value does not cause the roof, plumbing or electrical system to become proportionally more expensive to maintain.

AHURI's modelling assumed that land typically represents 57% of total property value in major cities and 39% in other areas. This helps explain why a percentage of market value is a broad benchmark rather than a precise maintenance forecast.

The insured value of the building may appear to be a closer reference because it is connected to the physical property rather than the land. It still needs careful interpretation.

Home building insurance is generally based on the cost to rebuild, not the market value of the property. The sum insured may also need to cover demolition, site clean-up, council fees, architect and surveyor services and temporary accommodation. Those costs belong to a total-loss scenario and do not necessarily reflect the cost of ordinary upkeep.

An insured value says something useful about the building's replacement complexity. It does not predict maintenance in a typical year.

Market value, insured value and maintenance history are three different views of the same property. None should be silently substituted for another.

A percentage can begin the budget, but it cannot finish it

A percentage-based allowance can help an owner create an initial expectation.

The property's own records gradually provide a better answer.

The insurance renewal shows what cover cost this year. The plumber's invoice records the repair that was actually completed. The rates notice captures a recurring obligation. A maintenance receipt becomes part of the longer history of looking after the property.

As these records accumulate, the budget moves from a general estimate towards an account of the property itself.

That history can show what was expected, what was paid, which costs recur, where expenses are changing and which documents support each figure.

The purpose is not to turn every owner into an accountant. It is to make the property easier to understand.

Let expenses arrive the way they already do

Every property registered with House Spek has its own Property Budget, inside the property's Logbook.

An expense can be added in the way that best matches how it arrived.

Upload the document. Add an invoice, receipt, rates notice or insurance document to the Logbook with AI Assisted Upload. When House Spek finds a regular cost in it, such as an insurance premium or a rates instalment, it offers that cost to the Property Budget, already connected to the document it came from.

Enter the figure manually. Regular payments, known allowances and costs without a document can be recorded directly, and linked to a document in the Logbook whenever one exists.

Forward the email. Every registered property has its own email address. When a property expense arrives by email, forward it there and it arrives in Property Mail, where it can be reviewed before it is filed to the Logbook.

These options do not remove the changing nature of property expenses. They give those changes somewhere to be seen together.

Know what the property costs, not just what you paid for it

The purchase price records one moment.

The cost of owning, maintaining and improving a property develops over years. It is found across repayments, rates, insurance, maintenance, repairs and the smaller expenses that rarely arrive together.

Research can suggest an allowance. Market value can provide context. Insured value can describe the scale of rebuilding. The most relevant picture is created by the property's own history.

Sources

• Cotality, Housing Affordability Report, November 2025
• Reserve Bank of Australia, Is Housing Overvalued?
• Australian Housing and Urban Research Institute, Shared equity programs in Australia
• Allianz Australia, Home Care Report 2025
• ASIC Moneysmart, Home underinsurance

House Spek provides tools for organising property information. It does not provide financial advice or estimate the maintenance needs of an individual property.