When you buy a house with a partner you’re not married to, you’re splitting one house, but the law treats you as strangers.
Couples who aren’t married but buy a house together make two separate bets at once. The first is on the relationship. The second is on their ability to navigate a legal structure that was never designed for them. Most people only think about the first bet. The second one is where the money disappears.
The immediate appeal is obvious: pooling income makes approval easier, shared expenses make the monthly payment manageable, and you’re already living together anyway. But a mortgage doesn’t care about your relationship status. It treats both of you as equally liable for the full debt, while property law treats you as business partners who happen to share a bedroom.
That gap between liability and ownership creates a minefield that married couples never have to worry about.
The Ownership Structure Nobody Explains Clearly
When you’re not married, you don’t get the default protections that come with spousal property rights. Instead, you have to choose how you’ll hold title, and most couples pick whatever their real estate agent mentions first without understanding what it actually means.
Joint tenancy with right of survivorship sounds romantic. If one person dies, the other automatically inherits their share. But it also means you can’t sell or mortgage your half without the other person’s consent, and in some states, one partner can unilaterally sever the joint tenancy and convert it to tenants in common without even telling you.
Tenants in common gives each person a defined ownership percentage and the freedom to sell their share independently. It also means if one partner dies, their share goes to their estate, not to you. If your partner’s family doesn’t like you, you could end up co-owning your home with their parents or siblings.
Neither structure protects you the way marriage does. And neither one addresses what happens when the relationship ends but neither person can afford to buy out the other.
The Breakup Math That Destroys Equity
Here’s the scenario that plays out constantly: you split up after three years. You’ve built equity between appreciation and principal paydown—the exact amount varies wildly depending on your market, purchase price, and interest rate, but let’s say it’s substantial enough that losing half of it would sting. One person wants to stay, the other wants out.
If you were married, divorce court would handle the division and force a sale or refinance if necessary. When you’re not married, there’s no automatic legal process. You have to either agree voluntarily or file a partition action, which is a lawsuit that forces the sale of the property and splits the proceeds.
The cost of partition actions varies significantly based on complexity and local legal rates. A simple, uncontested partition might run a few thousand dollars in legal fees. But if there’s disagreement about contribution amounts, improvements made, or who should get the property, costs can escalate to $15,000, $30,000, or more as the case drags through court. According to the American Bar Association, contested real estate litigation routinely consumes 10-20% of the property value in legal fees and court costs. In a moderately contested case, you can lose a substantial portion of your equity just getting out of the house.
And if one partner contributed more to the down payment or made all the mortgage payments for the last year while the other was “figuring things out,” the court doesn’t care unless you have written documentation proving it was a loan, not a gift.
Verbal agreements mean nothing here. If you handed your partner $20,000 toward the down payment without a written contract specifying it was a loan with repayment terms, the law treats it as a gift. You don’t get it back.
The Liability That Doesn’t Split
Both names on the mortgage means both people are 100% liable for the full debt. If your partner stops paying, the lender doesn’t care about your relationship status or your internal agreement about who owes what. They’ll come after both of you, and both credit scores get destroyed equally.
This isn’t like splitting rent. If your ex stops paying their half of the rent, you can choose whether to cover it or just let the landlord evict both of you. If your ex stops paying their half of the mortgage, your only options are to pay the full amount yourself or let the house go into foreclosure, which wrecks your ability to buy another home for years.
Refinancing to remove one person from the loan requires qualifying on a single income, which most people can’t do. That means even if you agree on a buyout price, the person staying often can’t actually execute it without finding a co-signer or waiting years to build enough income.
In the meantime, the person who wants out is still legally tied to the mortgage. They can’t qualify for another home loan because their debt-to-income ratio includes the existing mortgage. They’re financially stuck in a relationship that’s already over.
The Down Payment That Becomes a Gift
The most common financial arrangement is one person putting up most or all of the down payment while both incomes qualify for the loan. Maybe one partner has been saving for years while the other is still paying off student debt. Maybe one received family money. Either way, the assumption is usually that the person who paid more has some claim to a larger share.
Legally, that assumption is wrong unless you document it in writing before you buy.
If you put down $60,000 and your partner put down nothing, but you take title as joint tenants, you each own 50%. If you break up and sell, you split the proceeds evenly, and your extra $60,000 is just gone. The only way to protect it is with a cohabitation agreement or property agreement signed before the purchase that specifies how contributions will be handled in the event of a split.
Most couples don’t do this because it feels unromantic or because they assume “we’ll figure it out if it comes to that.” By the time it comes to that, the money is already pooled and legally indistinguishable.
When It Makes Sense Anyway
There are situations where buying together while unmarried is defensible, but they all require deliberate legal protection.
If both partners have stable income, roughly equal financial contribution, and a written cohabitation agreement that specifies ownership percentages, buyout procedures, and what happens if someone stops paying, the structural risks become manageable. If you’re in a state that recognizes domestic partnerships with some property protections, that helps. If you’re planning to marry soon and view the house as the first step, the timeline risk is shorter.
The calculation also changes if you’re buying a cheaper property you could each afford alone if needed. If the mortgage payment is low enough that one person could realistically cover it and refinance solo within a year or two, the exit risk drops significantly.
But if you’re stretching to qualify using both incomes, if one partner is contributing far more than the other, or if you haven’t had an explicit conversation about what happens if you break up, you’re not making a financial decision—you’re just hoping the relationship works out and assuming you’ll deal with the consequences later.
The Agreement That Actually Protects You
A cohabitation agreement is the only tool that converts legal ambiguity into enforceable protection. Cost varies by jurisdiction and complexity—simple agreements using attorney-reviewed templates might run $500-$1,500, while comprehensive agreements drafted by family law attorneys in high-cost areas can exceed $3,000-$5,000, according to legal directories like Nolo and the National Association of Consumer Advocates.
The agreement should specify exact ownership percentages, how equity will be divided, who gets the option to buy out the other, how the buyout price will be determined, what happens if one person can’t pay, and what happens if one person dies.
It should also address ongoing contributions: what if one person loses their job and stops paying the mortgage for six months? Is that treated as a loan to be repaid, or does it adjust their ownership share? What if one person pays for a $30,000 kitchen renovation—do they get that money back, or does it just increase the home’s value for both of you equally?
These sound like pessimistic questions, but they’re the exact issues that turn into five-figure legal bills when you don’t answer them in advance.
The agreement doesn’t prevent breakups, but it does prevent the breakup from becoming a financial disaster. It converts an emotional negotiation into a contractual one, which is the only way to protect equity when the law won’t do it for you.
The Comparison Nobody Makes
Buying a house before marriage introduces similar risks but with a different timeline—you’re expecting to marry soon, so the legal ambiguity is temporary. Buying with a non-romantic partner, like a friend or family member, actually has clearer boundaries because there’s no emotional assumption that “we’ll work it out.”
The romantic relationship without marriage is the worst of both worlds: the legal exposure of a business partnership combined with the emotional complications of a breakup.
This mistake first-time home buyers make often involves underestimating transaction costs and overestimating how long they’ll stay. When you add relationship risk on top of market risk, the break-even timeline extends even further, and the odds of hitting it drop.
The Real Trade-Off
Buying a house together while unmarried works if you treat it like the legal partnership it actually is: documented, specific, and unsentimental. It fails when you treat it like a commitment ceremony with a mortgage attached.
The decision isn’t really about whether your relationship will last. It’s about whether you’re willing to spend the money and have the uncomfortable conversations that protect you if it doesn’t. Most people aren’t. They’d rather believe the relationship is strong enough that legal protections are unnecessary, which is exactly the belief that costs them tens of thousands of dollars later.
If you’re not ready to sign a cohabitation agreement, you’re not ready to co-own a house. And if your partner refuses to sign one, that’s not a sign of trust—it’s a sign they haven’t thought through what happens when things go wrong, which means you’ll be the one paying for that lack of planning when they do.
Are you prepared to buy out your partner if the relationship ends, or are you assuming you’ll both just agree to sell and split it fairly?