The [tenants guide][1] distributed by the California courts
addresses this (partially) on p. 21
> The rental agreement may be oral or written, however, it is strongly
> recommended that the parties have a written rental agreement. The
> landlord is required to provide the tenant with a signed copy of the
> rental agreement within 15 days of its execution. The landlord and
> tenant should retain copies of the signed rental agreement for their
> records. An oral agreement is an agreement where the terms are agreed
> upon by spoken communication. This is in contrast to a written
> agreement where the terms are set forth in a written document. A
> tenancy term of more than one year must be in writing. Oral agreements
> for a tenancy term of more than a year are unenforceable.
Text messages are a form of writing. However, looking at the bits of code in the associated footnote, [Cal. Civ. 1624][2]
> (a) The following contracts are invalid, unless they, or some note or
> memorandum thereof, are in writing and subscribed by the party to be
> charged or by the party’s agent: ... (3) An agreement for the leasing
> for a longer period than one year, or for the sale of real property,
> or of an interest therein; such an agreement, if made by an agent of
> the party sought to be charged, is invalid, unless the authority of
> the agent is in writing, subscribed by the party sought to be charged.
("subscribed" means signed). An unsigned written 2 year lease is invalid, so by default the only lease that exists is a month-to-month lease. That is sort of what the attorney was saying.
One other issue is that para (d) says
> An electronic message of an ephemeral nature that is not designed to
> be retained or to create a permanent record, including, but not
> limited to, a text message or instant message format communication, is
> insufficient under this title to constitute a contract to convey real
> property, in the absence of a written confirmation that conforms to
> the requirements of subparagraph (B) of paragraph (3) of subdivision
> (b).
It's not obvious that text messages are "ephemeral", but the statute suggests that they are, and text messages are *not* legally binding as contracts in California, at least those subject to the requirement to be in writing.
[1]: https://www.courts.ca.gov/documents/California-Tenants-Guide.pdf
[2]: https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=CIV§ionNum=1624.