Nonmarital cohabitation (i.e. no marriage between parties, or no validly registered domestic partnership), does not itself confer rights or obligations under the Family Code. Any rights and obligations arising from the relationship may only be adjudicated in a general civil action.
No community, quasi-community or “quasi-marital” property rights, interests or obligations accrue during the term of a purely nonmarital cohabitation relationship that has not become a registered domestic partnership [Marvin v. Marvin (1976)]. A boyfriend living in the condominium owned by his girlfriend does not have any legal right to the girlfriend’s property, unless they have a valid contract or agreement that would indicate otherwise.
Registered domestic partners in California have almost all of the rights, benefits, protections and obligations that apply to spouses under California law both during and upon termination of the union, as per the California Domestic Partner Rights and Responsibilities Act [Stats. 2003, Ch. 421], and the Family Code [Fam.C. § 297.5]. Therefore, the same marital property rights that apply to married couples may also apply to domestic partners.
A separate property [Fam.C. § 770] of one of the domestic partners is his/her exclusive property. Unless statute provides otherwise, separate property and separate property interests are subject to the owner spouse’s exclusive management and control [Fam.C. § 752].
To become more informed about marital/domestic partnership property rights, it is best to consult with an expert in Family Law.