Co-Buying a House: How to Buy a Home with a Partner, Friend, or Family Member

Property prices have moved far enough beyond single-income reach in most major cities that co-buying — purchasing a home jointly with a partner, friend, sibling, or parent — has shifted from an unusual arrangement to a standard strategy. In Australia, 60% of first-time buyers now purchase with someone else. In Canada, co-buying with a non-spousal partner is increasingly common as a workaround for unaffordable markets.

The financial case for co-buying is clear: combined incomes, combined savings, and a shared mortgage burden. The complications arise when the legal and financial structure isn't set up properly from the start. This piece covers what you need to know before signing anything.

Types of Co-Buying Arrangements

Spouses or domestic partners: The most legally protected form. Mortgage lenders treat this as the standard case. Property ownership is typically joint tenancy (survivorship rights to the other partner if one dies), though married couples can also hold property as tenants in common.

Unmarried couples: Common law, de facto, or simply dating cohabitants face more legal complexity. Without a cohabitation agreement, rights to the property in case of separation can become complicated. Legal structures must be deliberate.

Friends: Two or more friends purchasing together is a growing phenomenon in high-cost cities, particularly among buyers in their 30s who are not in romantic relationships. Legal structure and a co-ownership agreement are essential from day one.

Parent-child purchases: Parents often assist adult children in qualifying for a mortgage by co-signing or contributing to the down payment. This can be structured as joint ownership or as a gifted/loaned contribution to the child's purchase.

Siblings: Common in families where property is an intergenerational wealth strategy, or where siblings want to purchase in a market they couldn't afford individually.

The Two Forms of Joint Ownership

In common law jurisdictions (US, UK, Canada, Australia), property is typically held in one of two ways:

Joint tenancy: Both owners hold equal, undivided shares. If one owner dies, their share automatically passes to the surviving owner (right of survivorship), bypassing the deceased's estate and will. Cannot be sold independently.

Tenants in common: Each owner holds a specific, defined percentage of the property that can be different from the other owner's share. Each share can be sold, gifted, or inherited independently through the owner's estate. This is the more flexible structure for non-spousal co-buyers.

For friends or family members, tenants in common is usually the right choice. It allows unequal contribution splits to be reflected in unequal ownership percentages, and each person's share remains part of their estate.

Structuring the Down Payment When Contributions Are Unequal

This is where co-buying gets complicated. If one party contributes 70% of the down payment and the other contributes 30%, how is that reflected in ownership, the mortgage, and eventual sale proceeds?

Option 1: Equal ownership despite unequal contribution Both parties own 50% each. The party that contributed more effectively gives the other a gift of equity. This works fine for spouses with commingled finances; it creates serious issues if the co-buyers later separate.

Option 2: Ownership proportional to contribution Tenants in common, with each party's percentage reflecting their down payment contribution. If Partner A puts in 70% and Partner B puts in 30%, they own in those proportions. Sale proceeds are divided accordingly.

Option 3: Ownership with a recorded side agreement Both owners hold 50% in the title, but a separate legal agreement (registered with appropriate legal counsel) records the reimbursement owed to the higher-contributing party before proceeds are split. This maintains legal simplicity in ownership while preserving the financial equity of unequal contributions.

Option 4: One party as owner, one as lender Rather than joint ownership, one party (the primary buyer) purchases the property, and the other party provides a private loan for the down payment. The loan is documented, interest-bearing or interest-free, and recorded in a promissory note. This is common in parent-child arrangements where the parent doesn't want to be on the mortgage or title but wants their capital protected.

The Co-Ownership Agreement

Regardless of the legal ownership structure, a detailed co-ownership agreement drafted by a property attorney is non-negotiable. This agreement should address:

Expense allocation:

• How is the mortgage split? (Equal payments? Proportional to income? Proportional to ownership?)
• Who pays for ongoing maintenance, insurance, and property taxes?
• What's the process for major capital expenditures (new roof, HVAC)?

Decision-making:

• Can either party rent out their share without the other's consent?
• How are renovation decisions made?
• What happens if one owner wants to sell and the other doesn't?

Exit provisions:

• What if one owner wants to sell their share? (First right of refusal for the co-owner? Required appraisal? Mandatory buyout within X months?)
• What if one owner stops making payments?
• How is the property valued in a buyout?

Life events:

• What happens if one owner marries and their spouse wants to move in?
• What if one owner dies without a will?
• What if one owner faces bankruptcy?

These conversations are uncomfortable to have with friends or family in the excitement of a purchase. They are infinitely less uncomfortable than litigating them later.

Mortgage Qualification When Co-Buying

Lenders treat co-borrowers differently depending on who is on the mortgage application:

Both parties on the mortgage: Both incomes count, which helps qualify for a larger loan. But both credit scores affect the terms — lenders typically use the lower of the two scores to determine rate and eligibility. If one co-buyer has a significantly weaker credit profile, it may cost more than their income contribution is worth.

Only one party on the mortgage: Simplifies underwriting if one person has better credit or income. The non-borrowing party can still be on the title (tenants in common) without being on the loan. However, the non-borrowing party's income doesn't help qualification, and only the borrowing party is legally obligated on the debt.

In Australia, co-buyers can each access their First Home Super Saver Scheme balances — potentially contributing up to $50,000 each (combined $100,000) toward the deposit. In Canada, each co-buyer can make FHSA and Home Buyers' Plan withdrawals from their own accounts, combining up to $80,000 from FHSAs and $120,000 from HBP between two first-time buyers.

Managing Co-Buying Savings Before Purchase

When two people are saving toward a joint purchase, the behavioral complexities multiply. Different savings rates, different timelines, different risk tolerances, and different levels of urgency create friction in what should be a coordinated effort.

Practical framework:

• Agree on the target purchase price range and timeline in writing before joining finances
• Open a dedicated joint high-yield savings account specifically for the down payment
• Establish proportional automatic monthly contributions reflecting each party's agreed share
• Create a shared tracking document showing individual contributions, total balance, and progress toward the target

The Down Payment Savings Plan & Strategy Guide includes worksheets specifically designed for co-buyers — tracking unequal contribution scenarios, modeling different ownership split outcomes, and managing the combined savings toward a shared closing date.

Legal Counsel Is Not Optional

The cost of a property attorney to draft a co-ownership agreement is typically $500-$1,500 depending on complexity. The cost of litigating a disputed co-ownership in court is orders of magnitude higher. The discomfort of having the conversation is trivial compared to the risk of not having it.

Before signing any purchase contract in a co-buying arrangement, both parties should independently consult a property lawyer familiar with co-ownership in your jurisdiction. The discussion about what happens in every foreseeable scenario should happen before you fall in love with a house, not after.

The Bottom Line on Co-Buying

Co-buying expands the financial reach of both parties and can make homeownership achievable in markets that would otherwise require a decade of solo saving. The risks are real — financial disputes between co-owners are genuinely damaging to relationships — but they're manageable with proper legal structure, clear written agreements, and transparent communication about each party's financial situation and expectations.

The savings phase is actually the easiest part. Get the legal framework right from the start.