How Income Increases Affect Borrowing Power

Income boosts can reshape your home-loan capacity—but the effect isn’t always straightforward. In this case study, we track Mel and Ronald, a dual-income couple with a principal place of residence in Craigieburn and an investment property in Pimpama.

Financial Baseline

Gross Income: $154,000 / year
Net Income: ~$116,000 / year
Rental Income: $39,000 / year (80% assessable = $2,600 / month)
Total Assessable Income: ~$12,267 / month
Expenses (HEM): $4,000 / month
Loan & Debt Commitments: $7,079 / month
Surplus Income: $1,188 / month
Borrowing Power: ~$154,600 (assuming $768.70 / month per $100k at 8.5%)

Scenario Analysis: Income Increases

We modelled income rises of $10k, $20k, $50k and $100k, then calculated the revised net income, surplus income, unconstrained borrowing power and DTI-compliant loan limits.

Income Increase	Gross Income	Net Income	Surplus Income	Unconstrained Borrowing Power	DTI-Limited Loan	Purchasing Power (Loan + $194k Equity)
$0	$154,000	$116,000	$1,188	$154,600	$154,600	$348,600
$10,000	$164,000	$122,500	$1,729	$224,900	$0	$194,000
$20,000	$174,000	$129,000	$2,271	$295,300	$0	$194,000
$50,000	$204,000	$147,000	$3,771	$490,400	$40,000	$234,000
$100,000	$254,000	$176,000	$6,188	$804,900	$340,000	$534,000

Key Insights

DTI Bottleneck: Borrowing remains capped until combined income exceeds ~$236k. Beyond that, capacity jumps sharply.
Repayment Impact: At 6% interest, a $340,000 loan carries repayments of ~$2,038 / month. Even with existing debts, total outgoings stay manageable within the new income.
Borrowing Efficiency: Each $10k income boost adds ~$541–$629 in surplus, allowing an extra $70k–$80k in borrowings once DTI limits lift.

Chart: Borrowing Power vs. Income

Recommendations

Reduce Liabilities: Clearing small debts (e.g. Zip Pay) can boost borrowing power by over $100k.
Strategic Income Targets: A $50k raise only unlocks $40k extra borrowing due to DTI. A $100k jump makes a major difference.
Consult a Broker: Some lenders allow higher DTI ratios or more generous rental income assessments.
Use Borrowing Calculators:

Income growth can increase borrowing potential—but only when paired with manageable debt and lender flexibility. Mel and Ronald’s journey highlights how strategic planning and expert advice unlock better outcomes. Assess your borrowing potential and secure your path to financial success today.