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Model Off‑the‑Plan Apartment Cashflow Before You Sign Anything

Thinking of an off‑the‑plan investment apartment? Here’s a simple, decision‑grade way to model cashflow, stress‑test holding costs and decide if the deal still works when rates, rents and tax rules move.

Published 10 Sept 2026Updated 10 Sept 20265 min read

Key Takeaway

This article explains how to model cashflow for an off‑the‑plan investment apartment so investors can test affordability before signing. It recommends modelling at least three years post‑settlement with a 2–3% interest rate rise, 10–15% rent risk, and full holding costs, and notes lenders use a minimum 3% serviceability buffer (APRA). The key insight: if the property is not sustainable on pre‑tax cashflow under stress‑tested assumptions, the strategy should be changed or abandoned.

Model Off‑the‑Plan Apartment Cashflow Before You Sign Anything

This topic is covered in full on Tailored Loans Sydney

Thinking of an off‑the‑plan investment apartment? Here’s a simple, decision‑grade way to model cashflow, stress‑test holding costs and decide if the deal still works when rates, rents and tax rules move.

Read the full guide on tailoredloans.sydney

Before you sign an off‑the‑plan contract, you need a decision‑grade cashflow model showing: 1) the deposit phase, 2) year‑one holding costs, and 3) what happens if rates rise and rents wobble. If the deal only works with best‑case rent and tax refunds, it’s too fragile.

Here’s a simple way to build that model this week.

Cashflow spreadsheet for off-the-plan investment apartment on laptop Build a clear, three-year cashflow model before committing to an off-the-plan contract.

1. Map the off‑the‑plan timeline and risks

Off‑the‑plan is a three‑stage cashflow story:

  1. Deposit to settlement (18–36 months)
    • 10% deposit tied up.
    • No rent, but you may pay interest on borrowed deposit.
    • Construction risk: delays, rising levies/strata costs (recent ABS data shows building costs up ~3–4% p.a.).

  2. Settlement year
    • Full mortgage starts.
    • Fit‑out, blinds, furniture, utilities connections.
    • Leasing risk and possible initial vacancy.

  3. Steady state (years 2–3)
    • More stable rent.
    • Ongoing rate, strata and insurance increases.
    • Possible tax rule changes (the 2026–27 Budget proposals hit negative gearing and CGT).

Your model should cover today to three years after settlement, with at least one stressed scenario where interest rates are 2–3% higher and rent is 10–15% lower than you hope.

(If you’ve already got an investment unit, think of this as the same discipline we use when deciding whether to keep or sell, as in [/insights/keeping-alexandria-unit-when-you-upgrade-lender-rules-cashflow-tests].)

2. List every holding cost — not just the mortgage

Most investors underestimate non‑loan costs. Build a table for year one after settlement with these line items:

Loan and property costs

  • Interest: model both interest‑only and P&I options.
  • Principal (if P&I): remember this is cash out, even if it builds equity.
  • Council and water rates: often $2,000–$3,000 p.a. combined for an apartment.
  • Strata / body corporate: lift, gym, pool and concierge all add up. New builds can easily run $4,000–$8,000+ p.a.
  • Building insurance: usually in strata but check.
  • Land tax: if you already own property, model a conservative estimate.

Tenant and maintenance costs

  • Property management fees: often 5–8% + GST of rent, plus letting and inspection fees.
  • Initial leasing costs: advertising and letting 1–2 weeks’ rent.
  • Repairs, defects, small items: still assume at least $1,000–$1,500 p.a. once the first year of builder fixes passes.
  • Initial fit‑out: blinds, whitegoods, minor furnishings — often $5,000–$10,000 upfront.

Finance and admin

  • LMI (if >80% LVR): either capitalised or paid upfront.
  • Account‑keeping / package fees: $300–$400 p.a. per package is common.
  • Landlord insurance: $350–$800 p.a.

If you run a business, keep these clearly separated from business debts and cashflow, as outlined in [/insights/separating-business-investment-personal-debts-cleaner-borrowing].

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Frequently asked questions

For a new off-the-plan apartment, allow at least four weeks vacancy in year one, then two to three weeks per year after that. Lease-up can be slower when many similar units settle at once, so using conservative vacancy assumptions reduces the risk of nasty surprises and helps you size your cash buffer properly.
Yes, you should model both interest-only and principal-and-interest repayments. Interest-only periods are temporary and lenders are not obliged to extend them, especially if your circumstances change. Seeing the P&I numbers now helps you decide if the property will still be sustainable when principal starts or if you’d be forced to sell or refinance.
No, it’s risky to rely on tax refunds to make an investment property work. Tax rules, your income and government policy can change over a 5–10 year horizon. You should model the property on a pre-tax basis so it stands on its own cashflow, then treat any negative gearing or depreciation benefits as upside only.

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