Unlike many other areas of family law and contracts there are no specific laws (statutes) in California relating to surrogacy. However, California is considered a surrogacy friendly state and surrogacy here is common.
There are two kinds of surrogacy contracts, altruistic surrogacy and commercial surrogacy: both of which are recognized in California. In altruistic surrogacy contracts, the surrogcate is not monetarily compensated (by contract) for her services. These kinds of contrats are often created between friends and family. Commercial surrogacy is where a surrogate is paid for her services to carry the child. Compensation in commerical surrogacy is often a set number and the additional cost of pregnancy and labor is an added benefit for the surrogate (things like clothing, medication, pregnancy classes, to name a few).
There are also two kinds of surrogacy: traditional and gestational. Traditional surrogacy is when the surrogate contributes the egg that is then fertilized and carries the pregnancy to term, handing over the infant to the two other parents (who will legally be the parents). Gestational surrogacy is when an embryo is implated in the surrogate to carry to term: there is no biological relationship between the surrogate and the fetus.
California is also unique in that under the statutes governing the Uniform Parentage Act (commonly known as UPA cases or paternity cases) parents can legally establish their rights separate and apart from the surrogate prior to the birth. This is commonly known as a Pre-Birth Order (PBO). This is primarily done because without it, the surrogate gets listed as the mother; regardless if she is the biological or intended mother -- interestingly California defines the "mother" as the biological mother or gestational mother which in the past has complicated things. A PBO legally establishes the intended parents as such and helps clear up an potential complications following the birth of the child (or children).
Fortunately, California has evolved along with the quickly and ever changing definition of family, allowing for flexibility in how families are created and defined.
It is not uncommon for parties to seek guidance through surrogacy centers (there are many; faith based, LGBTQ friendly, etc.) who provide matches for surrogates and parents, legal assistance, contrats, etc. Seeking counseling through mental health providers is also recommended prior to any agreement for surrogacy.
It is always a good idea for parties to seek their own counsel individually (for example, the surrogate and the parents should each have seaparte attorneys) -- I am available for consultation on surrogacy and surrogacy contracts.