Locked vs Dynamic Equity: When One Co-Owner Pays More

The $30,000 Question

Your co-owner put an extra $30,000 toward the mortgage this year. They didn't mention it. They just did it.

Did they do you a favor, or did they just take something from you?

Neither of you can answer that yet. The answer was decided by something the two of you agreed to on the day you bought, and most co-owners don't remember agreeing to it. It comes down to whether your equity is locked or dynamic.

Two Ways to Own a House Together

There are two basic ways to structure ownership with another person.

Locked equity. Your percentages are set at closing and they never move. You own half, they own half, and that stays true no matter who pays what along the way.

Dynamic equity. Your percentages follow the money. Every dollar each of you puts in gets tracked, and ownership is whatever share of the total you've actually contributed. This is also called floating equity, or a capital account approach.

A co-ownership attorney we consult with says about nine out of ten deals that reach him involve two people bringing different amounts to the table. People who bring the same amount don't often call him. Of the clients who do, the large majority choose locked. Among the couples he works with, 30 to 40 percent choose dynamic.

Neither structure is wrong. They just produce very different results from the same payment. If you want the longer background on how contributions turn into ownership, our equity tracking guide covers the basics.

What the Extra Payment Does Under Each

Back to that $30,000.

Under locked equity, the payment knocked $30,000 off the mortgage. That's $30,000 more equity in the house, and you own half of it. Your co-owner spent $30,000, and $15,000 of it is now yours.

If nothing was written down about that payment, that's where it stays. It was a gift. If the plan was for that money to come back to them, as a loan, a credit, or anything else, it has to be documented when it's paid.

Under dynamic equity, nothing landed on your side at all. Their contributions went up, so their percentage went up, and yours went down. Say each of you had put $500,000 into a million-dollar house. After their extra $30,000, they've contributed $530,000 of $1,030,000, which is about 51.5 percent. Your 50 percent is now about 48.5.

Nobody did anything wrong. The system did exactly what you both set it up to do.

So dynamic equity sounds like the fair one. Put in more, own more. And if houses only ever went up, that would be the end of the story.

The House Goes Up and You Still Lose

Here is the part that's harder to see.

Take a house bought for $200,000 that later sells for $210,000. It gained value. The owners can still lose about 30 percent of what they put in.

Before anyone gets a dollar back, the cost of selling comes off the top. Call it 6.5 percent. Then the mortgage balance gets paid. Only what's left is equity, and it can be less than what the owners contributed.

Here is how the numbers work:

The house went up $10,000 and the owners lost $9,244.

Now the percentages decide who absorbs that loss. Suppose the ownership split on paper is 55/45, but the actual money contributed was 59/41. Splitting the $21,350 at 55/45 gives one owner $11,742.50 and the other $9,607.50. Against contributions of $18,050.46 and $12,543.54, that means one owner loses about 35 percent of their investment and the other loses about 23 percent.

Same house. Same sale. Same day.

That is the whole argument for one rule: ownership percentages should be based on contributions. When they aren't, a shared loss gets shared unevenly, and nobody notices until the closing statement arrives.

When a Bigger Share Is the Worse Share

Dynamic equity has its own catch. If the house is worth less than you owe on it, a bigger percentage isn't a win. A bigger share of an underwater house is a bigger share of the loss.

In that situation, the co-owner who paid extra didn't take anything from you. They volunteered for more of the damage.

This is why some owners who are willing to put in more money still don't want it to raise their percentage. The attorney described a client at 60 percent who would contribute more but refused to let it increase his share, because of the possibility of paying a larger share of the debt if the property sold at a loss. Instead, he offered to loan the money on agreed terms.

Gift, Loan, or Equity

That points to something useful. Money one owner pays beyond their share can only be one of three things:

1. A gift. It stays where it lands.
2. A loan. It comes back to the person who paid it, from the first money out at sale.
3. Equity. You agreed up front that paying more means owning more.

All three are fine. All three should be chosen before the money moves, not argued about after. This is the kind of conversation our post on talking about money with co-owners is meant to make easier.

The Order the Money Comes Back

Which brings you to the thing that actually decides who gets hurt when there isn't enough to go around: the order the money comes back.

A layered agreement sorts every dollar into one of three kinds:

• Money put in at closing. The down payment and closing costs.
• Money paid along the way beyond your share. Overpayments on the regular costs.
• Money put in after purchase by agreement. A new roof, a rescue payment, an improvement you both signed off on.

When there's a shortfall, they come back in reverse. After-purchase money first. Overpayments second. The down payment last. If a layer can't be repaid in full, the owners in that layer are repaid pro rata. Anything left after all three layers is split as profit by ownership percentage.

The reason for the order is incentive. When a property is in trouble, nobody wants to be the one who puts in more. So the agreement makes a promise: if you rescue it, your rescue money comes back first.

That means the money you put in on day one, the money that feels most like your stake, is the last money out. It's worth knowing that before you need to sell, and before anyone needs to exit the arrangement.

Two Things to Decide Before You Need Them

Most of the debate about locked versus dynamic equity is about a house that gains value. What actually decides who gets hurt is what happens when it doesn't. So settle two things while everyone is still happy.

First, a number that moves your ownership has to be agreed to before it moves. Not recorded afterward. Agreed before. One person shouldn't be able to enter a contribution alone and have it become true. That cuts both ways: neither owner gets to decide alone to pay less than their share, and neither gets to decide alone to pay more. A ledger only one of you keeps isn't a record. It's a grievance with dates on it.

Second, decide the order the money comes back on the day you buy. It's an easy conversation that day. It's a very different conversation on the day you sell.

If you're still at the planning stage, these belong on the same list as the other agreements to make before co-buying.

FAQ

What is the difference between locked and dynamic equity?

With locked equity, ownership percentages are set at closing and never move, no matter who pays what afterward. With dynamic equity, sometimes called floating equity, percentages follow the money: every dollar each owner puts in is tracked, and ownership is each person's share of the total actually contributed.

What happens if my co-owner pays an extra $30,000 toward the mortgage?

Under locked equity, the $30,000 adds $30,000 of equity to the house and you own half of it, so $15,000 of their payment becomes yours. If nothing was written down, it stays that way as a gift. Under dynamic equity, their percentage rises and yours falls. On a million-dollar house where each of you had contributed $500,000, 50/50 becomes roughly 51.5/48.5.

Can co-owners lose money even if the house goes up in value?

Yes. The cost of selling and the mortgage balance come off the top before anyone gets their contributions back. In one worked example, a house bought at $200,000 sells for $210,000 and the owners still lose about 30% of what they put in.

In what order do co-owners get their money back when there is a shortfall?

A layered agreement repays in reverse order of when the money went in: money contributed after purchase by agreement comes back first, then payments made beyond each owner's share, and the down payment and closing costs come back last.

Can one co-owner change the ownership split by paying more?

Not on their own. A number that moves ownership has to be agreed to by both owners before it moves. Neither owner should be able to pay more, or less, than their share alone and have it change the split.

Real Amigos is a tool to make co-ownership financial tracking simple, transparent, and automatic. Learn more about early access.

General information, not legal or tax advice.