Legal Question in Landlord & Tenant Law in California

The issue does not appear to be the existence of a rental agreement but your failure to pay your regular rent. If you catch up within the 3 days, you may remain in possession. If you do not, then the landlord can file an unlawful detainer lawsuit to have you evicted.

If there is no written lease, or formal oral agreement for a lease of less than a year, then a "tenanacy at will" is created when you rent property. The term of the tenancy at will is the same as the interval at which you agree to pay rent. So basically it is renewed every time you pay rent. That is all that is needed to have a tenancy. So whether you signed a lease or not is irrelevant. What is relevant, as Mr. Cohen points out, is whether you pay your late rent or not. If you do not, the landlord can then sue you for unlawful detainer, which will result in you being evicted and a judgment against you for the rent due and other damages.