Strategic Debt Reduction: How to Pay Off Your Family Home While Growing Your Rental Portfolio
- Joshua Flack
- Jun 3
- 3 min read
TL;DR
Not all debt is equal. Interest on your family home isn't tax-deductible. Interest on your rentals is. That single distinction drives one of the most powerful structuring strategies available: pay down the non-deductible home debt as fast as possible while keeping the deductible rental debt working. Done right, you reduce the debt that costs you the most after tax while still growing your portfolio. This post explains the mechanics.
Most people pay their debt down in the wrong order.
They throw spare money at whichever loan feels biggest or scariest. Usually that's the rentals. That's backwards. The debt you should be killing first is the debt that gives you nothing back: your family home.
The Core Distinction
Interest on borrowing for your owner-occupied home is not deductible. You pay it with after-tax dollars and get no tax benefit.
Interest on borrowing for income-producing rental property is deductible (back to 100% from April 2025). It reduces your taxable rental income.
So a dollar of home loan interest costs you more, in real terms, than a dollar of rental loan interest. Same rate, different after-tax cost.
The Strategy
The principle: direct your repayment firepower at non-deductible debt while keeping deductible debt intact.
In practice:
Pay your family home down aggressively, principal and interest, extra repayments where possible
Hold rental debt on structures that preserve deductibility
Don't pay rental loans down faster than the home, even though instinct says reduce all debt
This isn't about taking on more risk. It's about killing the expensive (after-tax) debt first.
The Offset and Revolving Credit Angle
Offset accounts and revolving credit facilities sharpen this further.
An offset account links your savings to your home loan, reducing the interest charged on the non-deductible debt without locking the money away. Your cash sits available, but while it sits there it's cutting your most expensive interest.
Used carefully, this accelerates home debt reduction while keeping flexibility. It needs discipline, the facility only works if you don't spend the buffer, but it's a powerful tool.
Worked Example
Two investors, identical positions. $400,000 home loan, $600,000 rental debt, $2,000 a month spare.
Investor A puts the $2,000 against rental debt. They reduce deductible debt, lose some deductions, and still carry the full non-deductible home loan.
Investor B puts the $2,000 against the home loan. They kill the non-deductible debt years faster, keep full rental deductions, and end up with the same total debt but in a far better structure.
Investor B is meaningfully ahead after tax, with no extra risk.
The Trap to Avoid
Don't restructure rental loans in ways that break deductibility chasing this strategy. The deductibility depends on what the borrowed money was used for (ie. the purpose of the funds). Moving money around carelessly can taint the deductible status. This is where structure advice matters.
Where This Leaves You
The order you pay debt in matters as much as how much you pay. Non-deductible home debt first, deductible rental debt held strategically. Same dollars, better outcome.
If your repayments are currently spread evenly or aimed at the rentals, you're leaving money on the table. Debt structure is where a good adviser pays for themselves many times over. The right structure costs nothing extra and saves you thousands a year.
At CRISP, we map your debt by deductibility and build a repayment structure that kills the expensive debt first while keeping the portfolio growing. It's one of the highest-value conversations we have.
Right debt, right order, right structure.
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About the Author:
Joshua Flack is a mortgage and lending adviser and the founder of Crisp Financial. Before finance, he spent two decades running businesses across construction, facilities services, and franchising, which is why his advice starts with how the numbers actually work rather than how the brochure says they should. He works with home buyers, investors, and self-employed borrowers across New Zealand, with particular depth in complex and non-standard lending. Crisp Financial Limited (FSP1012114) operates under the Link Financial Group FAP licence. The information in this article is general in nature and is not regulated financial advice.
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