RCW 26.16.120 allows for couples to make such agreements "to take effect upon the death of either." But does Washington State Law allow for such contracts to be executed and take place immediately upon execution of the agreement?
Divorce / Separation Lawyer
You may also want to review RCW 26.09.070 regarding separation contracts.
Though dated, a comprehensive review of Washington law about the validity of postnuptial agreements can be found in the Washington Law Review, vol. 54, p. 135 (1978).
Legal disclaimer: [In accordance with the Avvo community guidelines, this communication does not constitute "legal advice", nor does it form an attorney-client relationship.]
Washington allows for married couples to enter into private agreements concerning the nature of assets and liabilities that take effect upon execution and acknowledgment, but as RCW 26.16.120 states such agreements can be ignored by the court in certain circumstances (e.g., fraud or duress).
As with any contract, it is always a good idea to run it by an attorney prior to signing to make sure you have an agreement that you can enforced later on, especially if the agreement involves real estate.
I hope this helps.
Michele K. McNeill, Esq.
This answer provides general information based upon a limited set of facts and is not intended to create an attorney-client relationship or to be relied upon as legal advice.