You might want to post this in the Engineering Business Practice forum.
That said, in many states you need to registered as a business to sell engineering services, this is in addition to holding a PE.
Secondly, I would wager that in CA there are a boatload of additional requirements (seismic calacs) that scream for a local structural guy to do this.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube