Legal Question in Family Law in California

There is not really any standard form promissory note that would do what you want. In fact a note that does not have to be repaid unless they divorce may be void as against the public policy of this state that people be allowed to divorce if they can't get along. Even if it were a regular note payable over time, a due on divorce clause might be void.

If all you really care about, however, is that it be a joint debt to be paid out of community assets, then all you need is a simple promissory note with either monthly payments (or other regular payments), or just a due and payable by X-date, and then have both her and her husband sign it. Doing that while they are married will automatically make it a community debt. It will also give them the flexibility to assign it appropriately along with other assets and debts in the event of divorce. So for example, your daughter could take an extra share of the assets and take the entire debt to you, or they could pay it off, or he could take the debt to you to off-set him keeping a retirement account, etc.