A collection of answers to FAQs from below ...
1) This thread is for people who live in JUST ONE STATE, and that state is California.
Dual-residency or other multi-state residency questions are OFF TOPIC FOR THIS THREAD. We cannot know what any other state requires for considering a person a resident. But Federal residency is discussed exhaustively.
2) This thread is for people who have no kind of Federal Firearms License. We get questions about buying C&R weapons - if you have a C&R license, you can do what that license allows you to do in the other 49 states.
3) A number of people seem to want to move to California, but leave their guns behind, for an assortment of reasons.
BRING YOUR GUNS!
Once you actually move to CA, any guns you left behind in your previous state appear to have been transferred to whomever has them while you are in CA.
That means you can NOT go back and get them - that would seem to be an illegal interstate transfer, 'not-CA-resident' to CA-resident.
The effect of
Mance v Holder, the Texas case that ruled the restriction on out of state handgun purchase is unconstitutional (discussion
here) is not known as of March 6, 2015. Discussion of that case is off-topic in this thread until a clear application of the case is determined.