Short answer: in our worked example, a parent of three earning $100,000 could borrow only about $167,000 on one income. Add a partner earning about $49,000 four days a week and borrowing power jumps to about $592,000. With the 5% Deposit Scheme and the NSW stamp duty exemption, that buys a two-bed unit in Campbelltown at about $625,000, with roughly $33,000 down.
To make the numbers more fun, we ran them for Homer Simpson. In 1996 a house cost Homer about 5.6 years of pay. A Sydney median house today is closer to 15.
The borrower: one income, three kids
Australia has no nuclear power plants, so in Sydney Homer works as a health and safety advisor on about $100,000, around the Sydney average for the role. He supports a family of five and has a credit card he rarely uses.
How much can he borrow on his own?
About $167,000. Lenders deduct living costs for the whole family of five from his income, and they assess his credit card limit as a monthly debt even if the balance is $0. After the serviceability buffer, very little is left over for a loan. In Sydney, that is barely a granny flat.
Why a second income changes everything
Marge becomes a property manager four days a week, on about $49,000. Together they could borrow about $592,000, around 3.5 times more.
The reason: the family's living costs were already counted against Homer's income, leaving only about $1,400 a month spare. Almost all of Marge's take-home pay of about $3,550 a month adds straight to that surplus, and the surplus is what lenders use to size the loan.
The deposit: 5% with no LMI and no stamp duty
Price: about $625,000
Deposit: about $33,000
Loan: about $592,000
Lenders mortgage insurance: $0 under the 5% Deposit Scheme (otherwise about $22,900)
Stamp duty: $0 under the NSW First Home Buyers Assistance Scheme
Both schemes are subject to eligibility and price caps, and are for Australian citizens and permanent residents.
What it buys
A two-bed unit in Campbelltown. Bart and Lisa share a room, and Maggie gets the linen cupboard.
Then vs now
In 1996, Homer's payslip showed $479.60 a week, and a median new US home cost about 5.6 years of his pay. A Sydney median house of about $1.47 million is roughly 14.7 years of a $100,000 salary.
The takeaways
Dependants raise the living costs lenders assume, which lowers borrowing power on one income.
A second income, even part time, often adds far more borrowing power than its size suggests.
Unused credit card limits count against you.
Government schemes can cut the deposit and remove LMI and stamp duty for eligible buyers.
FAQs
How much can a family borrow on one income?
Much less than many expect. In our example, a $100,000 income with three children supported only about $167,000, because of the living costs lenders assume for a family of five.
Does part-time income count for a home loan?
Yes, permanent part-time income is usually counted in full. New or commission-based income may need more history.
Can families use the 5% Deposit Scheme?
Yes, if you meet the eligibility rules and the property is under the price cap for the area.
What could you borrow?
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Borrowing figures are estimates for illustration only, based on average salaries, lender living-cost benchmarks and the APRA serviceability buffer, as at October 2026. The family's circumstances are our assumptions. This is general information only and does not take into account your objectives, financial situation or needs. Subject to eligibility and lender credit criteria. Fees and charges apply. Your full financial needs and requirements need to be assessed prior to any offer or acceptance of a loan product.