Committed Intimate Relationships (CIR) – once called meretricious relationships or, in other jurisdictions, common law marriages – are fact-dependent. Generally speaking, the more financially integrated and stable the relationship has been over a length of time – the better chance that the court will consider your partnership a CIR. We like the Washington Law Help guide to Property Law for Unmarried Couples, if you are interested in some preliminary considerations: https://www.washingtonlawhelp.org/resource/washington-property-law-for-unmarried-couples.