Keep or Sell Your Old Home for a High‑End Upgrade?

Key Takeaway

To decide whether to keep or sell an existing home when upgrading to a high‑end property, borrowers should compare two scenarios with 2–3% higher interest rates, targeting total repayments below 30–35% of net household income. Key variables are deposit size, rental income realism, tax efficiency of loan splits, and cash buffers post‑settlement. The most robust plan keeps conservative gearing and at least 6–12 months of living costs in offset before committing to holding both properties.

You should keep your old home only if you can safely service both loans after your upgrade, keep at least 6–12 months of living costs in buffers, and the numbers still beat a clean sell‑and‑upgrade scenario after tax and costs. If holding both pushes total repayments above roughly 30–35% of net income or wipes out your cash buffer, selling (or staging the move) is usually the better call.

Australian couple comparing keep-or-sell home scenarios at their dining table. Map both ‘keep’ and ‘sell’ scenarios side by side before committing.

Step 1: Frame the decision with two clear scenarios

Always compare two worked cases before you get emotionally attached:

Sell, then upgrade – one mortgage, bigger deposit, lower risk.
Keep and convert to investment – two mortgages, rent plus tax benefits, higher complexity and risk.

Quick numeric example

Assume:

Current home value: $1.8m, loan $800k, P&I 25 years
Target home: $3.2m
Combined net household income: $28k per month

Scenario A – Sell:

Sell for $1.8m, clear $800k debt and say $80k in selling costs.
Net cash: ~$920k.
Put $800k into the new home as deposit and keep $120k buffer.
New loan: $2.4m.

Scenario B – Keep:

Keep $800k loan on old home, expected rent $1,350/week.
New home: 20% deposit from savings/equity, new loan say $2.6m.

Now stress‑test both at 2–3% higher rates than today.

If total repayments in Scenario B are heading north of 30–35% of net income and your buffer shrinks below 6–12 months of living plus mortgage costs, the “keep” plan is probably too thin (see facts 2, 6, 7, 11 above).

Step 2: Run the key numbers that change the answer

Four numbers usually swing the decision. ### 1. Total repayments under stress Model both scenarios at a rate 2–3% above today. For example, if: - $2.4m home loan at an indicative 6.5% over 25 years ≈ $16,200/month. - Add $800k investment loan at 6.9% IO ≈ $4,600/month. You’re at $20,800/month before rent. On $28k net income, that’s ~74% of income if the investment is vacant, and still heavy even with full rent. That’s well above a prudent internal cap of 35% of net income for geared professionals. ### 2. Realistic…

Frequently asked questions

Is turning my current home into an investment always better than selling?▾

No. It only makes sense if the property is a strong long‑term investment and your cashflow remains resilient under higher rates and rental shocks. Many high‑income households are better off selling a mediocre asset, upgrading cleanly, and later buying a purpose‑built investment when their buffers are strong and structure is optimised.

How much cash buffer should I keep if I hold both properties?▾

Aim for at least 6–12 months of all living costs plus both mortgages in offset or accessible cash. With large loans this can easily run into the hundreds of thousands. Treat bonuses or business windfalls as buffer and debt‑reduction capital, not income you rely on to meet core repayments.

Does cross‑collateralising the old and new homes matter?▾

Yes. Cross‑collateralising can tie both properties into one facility, limiting flexibility to sell or refinance later. It’s usually safer to keep loans separated by property and by purpose, which makes tax outcomes clearer and gives more options if markets or your circumstances change.

Speak with a specialist advisor

Confidential consultation, bespoke advice for your situation.

Should You Keep or Sell Your Old Home for a High‑End Upgrade?