All following contracts require written form for enforceability in California except:

The purchase and sale agreement for real estate must be in writing under California's Statute of Frauds (Civil Code §1624) as it involves an interest in real property worth more than $500.

Listing agreements must be in writing under California Civil Code §1624 and the Real Estate Law as they create an agency relationship involving real property for more than one year.

A buyer loan payment agreement secured by property lien must be in writing as it creates a security interest in real property, which falls under the Statute of Frauds requirements.