Two people buy a house together. One puts in the down payment, the other does the renovation work over four years. The deed has one name on it because that was simpler at closing. Nobody thought about it again.

Six years later they separate, and the partner who spent four years of weekends rebuilding a kitchen discovers what the deed actually means.

The Assumption That Causes the Problem

Many long-term unmarried couples operate on a belief that enough time together produces something like marital rights automatically. It generally does not.

Without marriage or an agreement, the default rules are largely about title and contract. Property titled in one partner's name is generally that partner's property, whatever the other contributed in money or labor, and there is no automatic division of what was built together.

Montana and Common-Law Marriage

Montana is among the states that recognize common-law marriage where specific conditions are met. This is genuinely important and it cuts in both directions.

For some couples it means they may have more legal status than they realized. For others it means a partner may later assert a marriage they do not believe existed, which is its own dispute.

Whether a given relationship meets the requirements is fact-specific and not something to assume in either direction. A cohabitation agreement can address the couple's intent on this directly, which is one of the more valuable things it does.

What an Agreement Can Cover

  • Property ownership, including who owns what regardless of whose name is on the title.
  • Contributions, including how a down payment, mortgage payments, or renovation labor are treated.
  • Shared expenses and how joint accounts are handled.
  • What happens on separation, including whether one partner may buy out the other and how the property is valued.
  • Debt, and who is responsible for what.
  • Intent regarding marital status, addressing the common-law question directly.

What It Cannot Do

Agreements between adults about their own property are one thing. Children are another. Parentage, custody, parenting plans, and child support are governed by their own law, and a private agreement between partners does not control them. Those issues are addressed through parentage and custody proceedings if they arise.

Estate Planning Is a Separate Gap

This is the one that causes real harm, and it is not solved by a cohabitation agreement.

An unmarried partner generally has no default inheritance rights and no automatic authority to make medical decisions. If one partner dies or is incapacitated without documents in place, the other may find themselves with no legal standing at the worst possible moment, while the estate passes to relatives the deceased may not have spoken to in years.

A will, a durable power of attorney, and a healthcare directive address this. A cohabitation agreement does not substitute for them.

It Is Not a Sign of Distrust

Couples resist this conversation for the same reason people resist prenuptial agreements: it feels like planning for failure.

The more accurate framing is that you are choosing terms while you both care about being fair to each other, rather than leaving it to default rules neither of you selected. That conversation is considerably easier now than during a separation. Our prenuptial agreement page addresses the same instinct in the marriage context.

If you own property together, are contributing unequally, or simply want to know what your position actually is, call 406-830-3060.