Flatmate & Boarder Income: A Straightforward Guide to Mortgage Lending Rules in NZ

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.

When you are looking to boost your borrowing power for a home loan, planning to get a flatmate is a common and highly practical strategy. While you likely refer to them as flatmates, banks formally classify this arrangement as "boarder income" on a mortgage application.

Because this extra cash flow can directly increase the amount a bank is willing to lend you, lenders look closely at how you declare this income to ensure your application is realistic.

Here is a straightforward look at how the maths works for flatmate income, the strict bedroom rules you need to meet, and how this strategy can give you a massive financial head start on your home loan.

How banks calculate flatmate income for your mortgage

Lenders do not simply take the amount of rent you plan to charge and add it directly to your application dollar-for-dollar. Because flatmates can move out or rooms can sit vacant, banks apply a conservative buffer to protect your budget.

• Standard bank allowances: Most New Zealand banks will credit a flatmate's contribution at a fixed baseline—typically between $150 and $250 per week, per person, depending on the specific lender's internal policy.
• The deposit restriction: If you have a standard 20% deposit, banks are generally happy to count projected income from up to two flatmates. However, if you are applying for a low-deposit loan (with less than a 20% deposit), some banks will only allow you to claim for one flatmate, or they may exclude boarder income entirely.

The tax perk: IRD's standard-cost method

One of the biggest advantages of having flatmates (boarders) rather than a separate rental property is how the Inland Revenue Department (IRD) treats the income.

Matching your flatmate plans to the actual property

A core rule of a home loan application is that your projected living arrangements must match the physical reality of the house you are buying.

Use this quick guide to see exactly how many bedrooms your target property will need:

Note: The bank will only accept boarder income if your application clearly matches the number of spare bedrooms in the specific home you place an offer on.

Why flatmates are a massive financial advantage early on

Beyond just getting your mortgage approved, having a flatmate in the early days of your homeownership journey provides a serious financial tailwind.

When you first buy a house, a large portion of your early mortgage repayments goes strictly toward interest. By using that extra $200 a week from a flatmate to make additional principal payments on your loan, you can shave years off your mortgage and save tens of thousands of dollars in interest over the long run. It is one of the smartest ways to aggressively pay down your debt while your personal budget is still adjusting to the reality of owning a home.

Do you have to keep flatmates forever?

A common question buyers ask is: "Am I locked into having flatmates for the entire life of the mortgage?"

However, life evolves. Once the loan settles and you are living in the home, you aren't legally obligated to keep flatmates forever. From a practical budgeting perspective, many homeowners naturally transition to living alone (or reclaiming those spare bedrooms) once their personal income increases enough to easily cover the mortgage, or when they have paid down the loan balance enough that the monthly payments become much more comfortable.

Let's run your numbers

Using flatmate income is a completely legitimate, standard pathway to homeownership, provided the maths is grounded in reality and reflects your genuine living plans. It is a tool designed to get you across the starting line, backed by rules that ensure you aren't taking on more than you can realistically handle.

Want to see how a flatmate's contribution could realistically change your borrowing options? Get in touch with the team at Home Loan Factory today for a clear, transparent second opinion on your numbers.