A quick heads-up: The information in this article is designed as a general educational guide only and does not constitute personalised financial, tax, or legal advice. Because everyone's situation is unique (and bank policies change frequently), we recommend speaking with a licensed Financial Adviser to see how this applies to your specific circumstances. For full transparency on our terms of service, how we are remunerated by lenders, and any specific situations where a fee may apply, please read How We Get Paid.
For decades, the classic New Zealand property ladder felt like a straight line: buy a modest starter home, live in it for a few years, sell it, and tip the sale proceeds into a larger family home.
Today, more homeowners are choosing a different path: the 'keep and buy' approach.
Instead of selling their first property, they convert it into a rental and use the usable equity built up in its value to fund the deposit on their next home. By holding onto the original property, they transition from standard homeowners into property investors—letting tenants help service the debt while building long-term wealth across two properties.
Here is how banks view this structure, the equity thresholds you need to clear, and how to work out what you can realistically borrow.
How banks view your home once it becomes a rental
The moment you decide to move out and rent out your current property, the bank fundamentally changes how they classify it. It is no longer an owner-occupied home; it is an investment property.
Under standard New Zealand lending criteria, banks require a 30% equity buffer to remain in an existing investment property at all times. This means a bank will generally only allow you to borrow up to 70% of the property's current market value.
Any equity sitting above that 30% buffer line is your usable equity. This is the capital you can draw against to fund the deposit on your new family home.
See the numbers in action
Use the interactive tool below to see how the equity split works in real terms.
Enter the current estimated value of your home alongside your remaining mortgage balance. The tool will calculate your mandatory 30% equity buffer, show you your usable equity, and give you an idea of your purchasing power for your next home.
(Toggle the 'Buying a New Build' switch to see how your purchasing capacity changes if your next home is a new build, which typically requires a smaller deposit).
The four steps to restructuring your loans
Executing a keep and buy strategy follows a clear, structured sequence:
1. Confirming the property value
First, we must establish exactly what your current home is worth. Depending on the lender and your equity position, this is done via an automated desktop valuation (AVM) or a formal Registered Valuation. This confirms your total equity and establishes your mandatory 30% investment buffer.
2. The equity top-up
We apply to increase (top up) the lending secured against your existing home by the amount of your usable equity. The bank approves this facility and makes those funds available for your purchase. At this point, your original property is formally set up as an investment loan.
3. Transferring the deposit
That newly released capital becomes the cash deposit for your next home. For an existing owner-occupied house, lenders generally look for a 20% deposit, whereas a turnkey new build can often be secured with 10%.
4. Setting up the new mortgage
Because your deposit is funded through the equity top-up, the bank arranges a separate mortgage secured against the new family home to cover the rest of the purchase price.
Rental income and tax considerations
Extracting the deposit is only half of the equation. The key credit hurdle is proving to the bank that your household income can comfortably service two mortgages at once.
How rental income helps your borrowing power
You do not have to carry both mortgages purely on your personal salary. Because your first home will generate rent, the bank factors this cash flow into your affordability assessment.
Lenders typically scale rental income back (usually counting 70% to 75% of the gross rent) to allow for rates, insurance, maintenance, and potential vacancies. That discounted figure is then added to your salary, strengthening your overall borrowing power.
Structuring your debt for tax efficiency
Turning a home into a rental comes with specific tax considerations.
In New Zealand, mortgage interest deductibility rules are tied to the use of the borrowed funds, not which property the mortgage is secured against. If you top up the loan on your existing home to buy a personal residence, Inland Revenue generally treats that new borrowing as private debt rather than a business expense, but as always, check with your accountant before taking any action.
Structuring your facilities correctly from day one is essential. We strongly recommend speaking with a property-savvy accountant before drawing down funds to ensure your loans are structured cleanly.
Finding out what you can borrow
At Home Loan Factory, we run the same servicing models used by major New Zealand lenders. We can calculate your usable equity, model your combined household cash flow, and help you structure both loans safely.
Thinking about keeping your first home as an investment? Book a free upgrade strategy session with a Home Loan Factory adviser today.
Frequently asked questions
Can I use equity from my current home to buy another and rent the first one?
Often, yes. This is often referred to as leveraging. By restructuring your existing mortgage, you can release the usable equity from your first home to act as the deposit for your next primary residence, keeping the first property as a rental.
How much equity do I need to keep my house as a rental?
Standard bank rules require you to leave at least a 30% equity buffer in an existing residential investment property. Your usable equity is whatever remains above that 30% line after deducting your current mortgage balance.
Will the rental income cover both mortgages?
Rental income from your first house helps service the debt on that property, but it rarely covers the full cost of both homes. The bank will factor in a shaded portion of your expected rent (typically 70% to 75%) alongside your personal income to test whether you can service both loans under their standard test rates.
