Stress‑Test Your Green Square Portfolio Before the Market Does

Most Green Square investors I meet have a spreadsheet; very few have a real cashflow model. On paper they “hold comfortably”. Under a 2–3% rate rise, one long vacancy or a new tax rule, the same portfolio can become a stress machine.

Cashflow modelling for multiple Green Square and city apartments means building a property‑by‑property, after‑tax picture of how your portfolio behaves when interest rates rise, rents fall, or your income drops – and then deciding now which levers you’ll pull if those scenarios arrive. Done properly, it’s the difference between choosing to sell an under‑performing unit and being forced to dump your best asset in a panic.

What I tell my clients: treat each apartment like a small business line. If it can’t stand on its own numbers under pressure, it’s not truly an investment, it’s a liability waiting for a trigger.

1. The real risk with clustered Green Square and city units

A recent client couple held three inner‑south apartments: two in Green Square, one in the CBD. All geared at 80–90% LVR, all interest‑only, rents strong – on today’s assumptions.

When we modelled:

1. Rates 2% higher than now,
2. One apartment vacant for three months,
3. Their tech contractor income down 25%,

…their comfortable surplus turned into a monthly $2,500 shortfall. Their risk wasn’t “the market”; it was a lack of detail.

The mistake I see most

Investors with multiple Green Square or Zetland apartments often:

• Rely on bank serviceability calculators instead of their own cashflow model.
• Assume today’s rent and incentives will last.
• Ignore building‑specific risks like high investor ratios and oversupply.

As I unpack in /insights/oversupply-incentives-investor-ratios-green-square-lending, some Green Square buildings sit in a harsher risk bucket with tighter LVR caps and more conservative rent shading. Your model has to respect that.

What “decision‑grade” modelling means

For a portfolio of Green Square and city apartments, your model should:

1. Stand alone, property by property – each unit is its own P&L.
2. Show pre‑tax and after‑tax cashflow (see principle 14 in the knowledge hub).
3. Stress‑test rates, rent and your income (at least 2–3% higher rates and 10–20% lower rent).
4. Link to buffers – how long can you last with no panic moves?
5. Produce a decision – hold, refinance, reprice, or sell.

If your spreadsheet doesn’t get you to a clear “if X happens, we’ll do Y”, it’s not finished.

2. Step one: build a clean schedule of your apartments

Start with a simple table summarising your Green Square and city units.

Use your actual loan balances and rates. If you’re not sure of the true all‑in rate, assume 0.2–0.3% higher than the headline for safety.

Start with a clean schedule of every apartment, then layer in realistic assumptions.

Key data points you must capture

For each property, list:

• Loan balance and term
• Repayment type: interest‑only (IO) or principal & interest (P&I)
• Current rate and any expiry dates for fixed/IO periods
• Weekly rent and how much is actually hitting your account after agent fees
• Strata, council, water, landlord insurance, and an allowance for repairs (I often start at 5% of rent)

If you own via SMSF, company or trust, record that as well. As I’ve written in /insights/smsf-company-trust-borrowing-specialist-vs-generalist, once entity borrowing is involved, lenders start viewing your whole world as one ecosystem.

3. Step two: calculate true pre‑tax cashflow per property

Now turn that table into a simple P&L for each unit.

Worked example: Zetland investment unit

Assumptions (illustrative only):

• Purchase price: $900,000
• Loan: $720,000 (80% LVR), interest‑only at 6.5%
• Weekly rent: $900 (gross)
• Agent + letting fees: 7% of rent
• Strata, rates, insurance: $7,000 p.a.
• Repairs/allowance: 5% of rent

1. Annual rent
$900 × 52 = $46,800

2. Non‑finance expenses
Agent fees (7%): $46,800 × 7% = $3,276
Repairs (5%): $46,800 × 5% = $2,340
Strata/rates/insurance: $7,000
Total non‑finance: $12,616

3. Net operating income (before interest)
$46,800 − $12,616 = $34,184

4. Interest cost (pre‑tax)
$720,000 × 6.5% = $46,800

5. Pre‑tax cashflow (before depreciation)
$34,184 − $46,800 = −$12,616 per year
≈ −$1,051 per month out of pocket.

That’s before tax effects. This is why principle 14 – modelling both pre‑tax and after‑tax cashflow – matters.

Add a conservative tax layer

If you’re on a 37% marginal rate and the property makes a $12,616 loss (ignoring depreciation), the tax saving is roughly:

$12,616 × 37% ≈ $4,667

So after tax, the cashflow shortfall is:

$12,616 − $4,667 ≈ $7,949 per year
≈ $662 per month.

Important:

• Don’t rely on negative gearing staying as generous forever – the 2026–27 Budget discussions around investment tax settings showed how quickly rules can move (see CPA Australia’s analysis).
• Don’t let a tax refund hide a fragile portfolio. If your pre‑tax numbers are ugly, a tax offset is a band‑aid, not a cure.

Do this calculation for every property. You want a per‑unit monthly surplus or deficit, pre‑ and post‑tax.