Here’s a complete, ready-to-publish WordPress article on property co-ownership agreements in Australia. It’s written in a clear, conversational tone and structured to help readers understand the costs, common mistakes, and key steps involved.
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You and a friend have found a property in Sydney’s inner west. Between you, the deposit is reachable, the repayments look manageable, and neither of you could afford it alone. It makes sense on paper. But without a co-ownership agreement, that same sensible arrangement can turn into a legal mess that costs more than the deposit ever did. A formal co-ownership deed typically runs between $500 and $4,000 depending on complexity, yet skipping it can trigger court-ordered partition proceedings that burn through five figures in legal fees alone. That gap matters whether you’re buying with a sibling, a business partner, or a friend.
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This article is general information only and does not constitute professional advice. For your specific situation, consult a qualified professional.
Co-ownership is becoming more common in Australia’s expensive markets because pooling resources is one of the few ways in. But the legal structure that works for a married couple buying a family home is rarely the right one for two friends or a parent helping an adult child. The difference comes down to how you hold the title and whether you’ve put the rules of your relationship on paper. Here’s what you actually need to know.
Four Things to Know About Co-Ownership Agreements
Australian property law recognises two forms of co-ownership: joint tenants and tenants in common. The one you choose changes everything about what happens if a co-owner dies, wants to sell, or stops paying their share.
What I tend to notice is that most people focus on the purchase price and forget the agreement until a problem shows up. The research makes it clear: the $500–$4,000 you spend on a solicitor-drafted deed is small compared to the cost of untangling a co-ownership breakdown without one. If you’re thinking about buying with someone other than a spouse, the timing of your purchase matters, but the structure of your ownership matters more.
The Real Cost of Co-Owning Without a Written Agreement
The headline figures are easy to find: a co-ownership agreement drafted by a solicitor costs somewhere between $500 and $4,000. The lower end covers a straightforward 50/50 split between two friends. The upper end handles complex arrangements with unequal contributions, multiple parties, or specific tax structures. But the real cost question is what happens without one.
If a dispute arises and no written agreement exists, the only remedy available is typically an application to the state Supreme Court under the Property Law Act for an order to sell and divide the proceeds. That process is litigation-heavy, slow, and expensive. Legal fees alone can run into five figures before the property is even sold. The court also has broad discretion on how the proceeds are split, which adds uncertainty on top of the cost.
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| Scenario | Typical cost | What you get |
|---|---|---|
| Co-ownership agreement (solicitor) | $500–$4,000 | Clear rules on shares, costs, exit, and dispute resolution |
| Court-ordered partition (no agreement) | $10,000–$50,000+ in legal fees | A forced sale controlled by the court, with unpredictable timing |
| Mediation (after dispute) | $2,000–$8,000 | A negotiated outcome, but no guarantee of agreement |
The numbers tell a clear story. Spending $1,500 on a proper agreement before settlement is a fraction of what a single court application costs. And the cost isn’t just financial. Court proceedings take months, during which the property can’t be sold, mortgage payments still need to be made, and relationships fracture.
One scenario that catches people out: a co-owner stops paying their share of the mortgage. Without an agreement, the other owner has to cover the full payment to avoid default, then try to recover the money through court. With an agreement, the default provisions are already written in, and the non-paying owner’s share can be bought out or sold under pre-agreed terms. That’s the difference between a manageable problem and a financial crisis. If you’re unsure about how different home loan structures affect co-owners, it’s worth understanding the full picture before signing anything.
Common Mistakes That Derail Property Co-Ownership
Choosing joint tenancy with a non-spouse
Joint tenancy means the surviving co-owner automatically inherits the whole property when the other dies. For friends, siblings, or business partners, that’s rarely what they want. If you die, your share goes to the other co-owner, not to your family or your will’s beneficiaries. The research is consistent: for non-spousal co-ownership, hold as tenants in common with a co-ownership deed. The fix is simple — tell your solicitor at the start that you want tenants in common with defined shares.
Assuming the mortgage liability matches your ownership share
Lenders treat all co-owners as jointly and severally liable for the full loan. If you own 30% of the property but the other owner stops paying, the bank can come after you for 100% of the mortgage. Your share on the title doesn’t limit your liability. An agreement can create a right for you to recover the extra amount from the other owner, but it doesn’t change the bank’s position. The only way to limit liability is a tenants in common loan where each party borrows separately — but these are uncommon and harder to arrange.
Not updating the agreement after a major change
Co-ownership isn’t a set-and-forget arrangement. If one person refinances, pays for major renovations, or changes their share of the mortgage payments, the agreement needs to reflect that. Without an update, the contributions recorded on the original deed become inaccurate, and a future dispute would default to the title percentages, not the reality of who paid what. The research advises updating the agreement whenever ownership shares, financial contributions, or refinancing changes occur.
Overlooking the tax treatment of your share
Each co-owner is taxed on their share of rental income and capital gains based on their ownership percentage, not their mortgage payments. If you own 70% of the property, you’re taxed on 70% of the rental income, even if you’re paying more than 70% of the loan. The same applies to capital gains when you sell. An accountant familiar with property and the specific co-ownership structure is essential — especially if one owner lives in the property and the other doesn’t, which affects the main residence exemption.
Of these mistakes, the mortgage liability gap is the one I see cause the most financial damage. A co-owner who thinks their 30% share limits their risk is in for a nasty surprise when the bank demands the full repayment. If you need legal advice on a co-ownership dispute, getting a clear picture of your liability is the first step.
Building a Co-Ownership Agreement That Works
A co-ownership agreement is a written contract separate from the property title. It doesn’t override the mortgage, but it creates enforceable rights between the co-owners. Here’s what a well-drafted agreement covers, in the order you’d typically address it.
Ownership shares and contribution breakdown
The agreement must state each person’s percentage share and document how it was calculated. That means listing the deposit, stamp duty, legal fees, renovation costs, and any other upfront contributions. If one person puts in a larger deposit, the shares should reflect that. The title records the percentage, and the agreement backs it up with the detail. Without this, a dispute over who contributed what can undermine the whole arrangement.
Financial obligations and cost-sharing mechanics
Mortgage repayments, council rates, water bills, insurance, body corporate fees, and maintenance costs all need to be assigned. The agreement should specify how each cost is split — by ownership percentage, equally, or by some other method. It should also cover what happens if one person can’t pay their share: a grace period, a right for the other owner to cover the shortfall and recover it later, and a default trigger that allows a buyout or sale. Offset accounts and extra repayments also need rules, since unequal contributions can shift the effective ownership balance over time.
Decision-making and day-to-day management
Who decides whether to renovate the kitchen? Who handles the rental if the property is an investment? The agreement should set a decision-making framework — unanimous for major decisions (selling, refinancing, structural changes), majority or individual for smaller ones. If the property is rented, one person may be designated as the property manager, or you can agree to use a third-party agent. The key is to avoid deadlock by specifying who has authority and what happens when opinions differ.
Exit provisions and dispute resolution
This is where most agreements are tested. The exit section should include a right of first refusal: if one owner wants to sell, they must offer their share to the other owners first at a market valuation. The valuation method should be agreed in advance — typically a licensed valuer chosen jointly. If the remaining owners don’t buy within a set period (say 60–90 days), the property can be sold on the open market. The agreement should also cover forced sale if none of the co-owners can buy out the exiting party. Dispute resolution should start with mediation, not court, to keep costs down.
Death and insolvency provisions
For tenants in common, each owner’s share passes to their estate or nominated beneficiaries. The agreement should state whether the surviving co-owners have the right to buy the deceased’s share from the estate, and at what valuation. For bankruptcy, the agreement should acknowledge that a bankrupt co-owner’s share vests in the trustee, who can compel a sale. Having these provisions in place avoids a forced sale on someone else’s terms.
What I’d do is treat the agreement as a non-negotiable part of the purchase costs, not an optional extra. The $500–$4,000 you spend on a solicitor — and each co-owner should have their own solicitor for independent advice — is the cheapest insurance you’ll ever buy for a property co-ownership. If you’re working through the stamp duty exemptions that might apply to your purchase, make sure the co-ownership agreement is on your list too.
Frequently Asked Questions About Co-Ownership
What happens if one co-owner stops paying the mortgage? ▾
Can I sell my share without the other owner’s permission? ▾
Do I need a separate solicitor from the other co-owner? ▾
Does a co-ownership agreement override the mortgage? ▾
What’s the difference between joint tenants and tenants in common? ▾
Can I use a template from the internet instead of a solicitor? ▾
What Happens If You Don’t Put It in Writing
The research is clear: without a co-ownership agreement, the only remedy for a dispute is a court-ordered partition — expensive, slow, and with no guarantee of a fair outcome. The cost of the agreement, spread across the co-owners, is a fraction of what a single court application costs. And the agreement doesn’t just protect you from the other owner. It protects you from the uncertainty of what happens when life changes: a death, a job loss, a relationship breakdown, or simply a change of mind. A well-drafted deed turns that uncertainty into a process you’ve already agreed on.
Remember: this article is general information only. For advice on your specific situation, speak to a qualified professional.
If this was useful, you might also want to read Escape the Rental Trap: Bold Strategies for Aussie Home Buyers.
Sources and Further Reading
The Future of Home Ownership in Australia: Trends and Predictions — A look at how co-ownership, shared equity, and alternative ownership models are reshaping the Australian property market.
Downsize to Upgrade Your Life: Rethinking Aussie Homeownership — Explores the trade-offs between owning a larger property outright and co-owning a more affordable one with flexibility.
Peakifi (2025). Co-ownership agreement guide. 🔗
Cockatoo (2025). Tenancy in common explained. 🔗
Agentbridge (2025). Co-ownership property Australia. 🔗
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