Legal Question in Real Estate Law in California

Re: deed of trust with assignment of rents

See my answer to your subsequent, slight more detailed, question.

The basic answer is that no one can encumber or sell property he doesn't own. In one co-owner signs, two things might happen: (1) the lender will take a hike; or (2) the lender will do the deal and accept only the signing co-owner's interest as the collateral.

Exceptions may exist, for example, where the signer is an agent or attorney in fact for the non-signer, or where a partnership is found to exist and own the property (irrespective of title being held in individual names) and the signer is a general partner with authority to act.