What Should Unmarried Co-Buyers Put in Writing Before Purchasing a House Together?

Unmarried co-buyers should put a written co-ownership agreement in place before closing that spells out how title will be held, how much each person contributed to the down payment, how monthly costs get split, what happens if one partner wants to sell or move out, and who inherits the property if one owner dies. California law doesn't automatically protect an unmarried partner the way it protects a spouse, so anything you haven't put in writing gets decided by default legal rules that may not match what either of you actually wants.

How Should Unmarried Co-Buyers Hold Title?

In California, co-buyers who don't specify otherwise are presumed to hold title as tenants in common, which means each person owns a defined percentage of the property, that share doesn't have to be 50/50, and there's no automatic right of survivorship. If one owner dies, their share goes through probate to their heirs, not automatically to their partner, unless a will, trust, or the deed itself says otherwise. The alternative is joint tenancy with right of survivorship, which passes the deceased owner's share directly to the surviving co-owner outside of probate, but requires equal ownership shares regardless of who actually put in more money. Neither option is automatically "better," but the choice has real consequences, and it should be a deliberate decision made with your escrow officer or an attorney, not something left to default.

What Should the Co-Ownership Agreement Say About Money?

The agreement should document exactly how much each person contributed to the down payment, closing costs, and any renovations, and whether an unequal contribution means an unequal ownership percentage or functions as a loan that gets repaid later. It should also spell out how ongoing costs, the mortgage, property taxes, insurance, HOA dues, and maintenance, get split each month, and what happens if one partner falls behind or stops paying altogether. Without this in writing, a partner who covers more than their share has no clean legal path to get reimbursed if the relationship ends.

What Happens If One Partner Wants to Sell or Move Out?

This is the scenario that causes the most conflict, and it's exactly what a co-ownership agreement is built to prevent. The agreement should set a buyout process: how the property gets appraised, how long the other partner has to arrange financing to buy out the departing partner's share, and what happens if neither partner can afford to buy the other out. Some agreements include a right of first refusal, giving the remaining partner the first chance to buy before the property goes on the open market. Without an agreement, a co-owner who wants out can file a partition action in court, which can force a sale of the property regardless of what the other owner wants, and the legal costs of that process come out of both owners' proceeds.

What Happens to the House If One Partner Dies?

If you're holding title as tenants in common without a will or trust, your share of the house doesn't automatically go to your partner, it goes through probate according to California's intestate succession laws, which prioritize blood relatives and legal spouses, not unmarried partners. If you want your partner to inherit your share, you need an estate plan that says so explicitly: a will, a living trust, or a transfer-on-death deed. Many unmarried co-buyers pair their purchase with term life insurance naming their partner as beneficiary, specifically so the surviving partner has funds available to buy out the deceased partner's heirs if needed.

Updated for September 2026.

Frequently Asked Questions

Do we need a lawyer to draft a co-ownership agreement, or can we write it ourselves?
You can draft the basic terms together, but it's worth having a California real estate or family law attorney review or draft the final agreement, especially the buyout and death provisions, since a poorly worded agreement can be just as costly to enforce as having none at all.

If we contributed unequal amounts to the down payment, does that automatically change our ownership percentage?
No, not automatically. Your ownership percentage is determined by what's stated on the deed and in any co-ownership agreement, not just by who paid what. If you want unequal contributions reflected in unequal ownership, that has to be documented explicitly.

Can one unmarried co-owner force the sale of the house if the other refuses?
Yes, through a partition action in court, which is one of the main reasons to have a buyout process spelled out in advance. A partition lawsuit can take months, costs both parties legal fees, and often results in a court-ordered sale at less favorable terms than a negotiated buyout would have produced.

Does registering as domestic partners change any of this?
Yes. Registered domestic partners in California receive many of the same community property rights as married couples, including survivorship rights, which changes the default legal outcome significantly compared to an unmarried, unregistered couple.

If you and your partner are thinking about buying a home together, I'm glad to walk through how title vesting and a co-ownership agreement fit into your specific purchase, and to connect you with an attorney who can draft the agreement itself.