Co-buying is the housing market's pressure valve: couples before marriage, friends pooling down payments, siblings buying together, parents going on title to strengthen a mortgage application. The law offers two main containers for shared ownership in both Canada and the US — joint tenancy and tenancy in common — and the choice between them decides what happens on death, on sale, and on falling-out. Most co-buyers let the choice happen by default at closing, and skip the co-ownership agreement entirely. Both omissions are cheap to fix on the way in and brutally expensive to litigate on the way out.
The two containers: survivorship or shares
The legal difference is one sentence with lifelong consequences. Joint tenancy carries the right of survivorship: when one owner dies, their interest passes automatically to the surviving joint tenant(s), outside the will, outside probate. Tenancy in common holds distinct shares — equal or unequal (60/40, 75/25, whatever reflects contributions) — and each owner's share passes through their estate to whomever their will names. The defaults follow the relationship in practice: spouses commonly choose joint tenancy (each wants the other to inherit seamlessly); friends, siblings, and investment partners almost always belong in tenancy in common (nobody intends their co-buyer, rather than their own family, to inherit their equity); parents helping adult children need actual advice, because putting a parent on title in either form creates tax, creditor, and estate consequences the mortgage broker never mentioned. The choice is recorded in the transfer/deed at closing — and if nobody chooses, jurisdiction-specific presumption rules choose for you, which is no way to decide who inherits a house.
What each choice means later — death, severance, and creditors
Three later moments reveal the choice's weight. Death: joint tenancy's survivorship overrides the will — a fact that surprises blended families constantly, when a house intended for children from a first marriage passes instead to the surviving co-owner. (Canadian courts add a wrinkle: a gratuitous transfer into joint tenancy with an adult child is presumed to be held in trust for the parent's estate unless a true gift is proven — documentation at the time decides later litigation.) Severance: joint tenancy is not a lock — either owner can generally sever it unilaterally into tenancy in common, sometimes without the other's knowledge, which estranged spouses' lawyers do routinely; anyone relying on survivorship should know it can quietly disappear. Creditors and life events: one owner's bankruptcy, judgment creditors, or divorce reaches their interest in either structure, dragging co-owners into proceedings they didn't start. None of these is a reason to avoid co-ownership; all are reasons to choose the container deliberately and paper the intentions when everyone is friendly and alive.
The co-ownership agreement: the document that prevents the lawsuit
- Money in: who paid what — down payment, closing costs — and whether unequal contributions mean unequal shares or a debt
- Money during: mortgage, taxes, insurance, repairs split how; what happens when someone can't pay their share
- Decisions: what needs unanimity (selling, renovating, renting) vs majority; how deadlocks break
- Exit: the buy-sell machinery — rights of first refusal, valuation method, timelines, and the forced-sale endgame if no one buys
- Life events: death (paired with wills and often life insurance), disability, relationship breakdown, a co-owner's bankruptcy
- Occupancy: who lives there, whether occupants pay rent to non-occupant owners, house rules for the shared asset
Without an agreement, the default exit in both countries is blunt: any co-owner can generally force a sale through court (partition proceedings), a remedy that works but arrives slowly, expensively, and with relationships already burned. The agreement exists to make sure nobody ever needs it — every scenario it covers is one that resolves by reading a clause instead of retaining counsel.
The special cases: couples, parents, and investors
Three configurations deserve their own paragraph. Unmarried couples: marriage brings property-division regimes; common-law relationships mostly do not (a few provinces excepted), so the title split and agreement are the property rights — document contributions honestly, because "we'll figure it out" is how one partner funds the other's equity for a decade. Parents on title: helping with qualification puts a parent into ownership, with consequences — potential loss of first-time buyer benefits and principal-residence tax treatment on the parent's share (capital gains on the child's home can become taxable to the parent), exposure of the home to the parent's creditors, and estate friction among siblings; often a guarantee, a documented loan, or a bare-trust arrangement with advice achieves the goal with fewer side effects. Friends and investors: treat it as the business it is — tenancy in common, a real agreement, and pre-agreed exits — because the data on friend co-ownership is the data on business partnerships: most work, and the ones that fail, fail on the scenario nobody wrote down.
Doing it right on the way in
The full setup, done properly, adds modest cost to a purchase already costing hundreds of thousands: a deliberate title election in the transfer documents; a co-ownership agreement drafted or reviewed by a lawyer (templates are a starting point; jurisdiction and tax details are where they fail); wills for every co-owner, because co-ownership without estate planning just relocates the ambiguity; a conversation with your lender, since co-borrowers are each fully liable for the whole mortgage regardless of the internal split — joint and several liability means the bank collects from whoever has money; and name-appropriate insurance including title coverage for all owners. An hour with a real estate lawyer at purchase, with everyone in the room and the awkward questions asked out loud, is the entire premium for decades of co-ownership that stays boring. Boring is the goal. Every interesting co-ownership story you have ever heard was missing a paragraph that could have been written for a few hundred dollars at closing.
Frequently Asked Questions
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