Moved to CA last week and separated after 4 yrs of marriage. Do I need to pay alimony? how much?

As a rule of thumb, the length of time you might be required to pay alimony, particularly when there are no kids, is the length of the marriage. The rationale for this is that the marriage takes one partner out of the labor market thus handicapping them when they seek to return. Alimony is designed to help them over the start-up period. That's the reasoning behind alimony/spousal support. But in your case I would guess the question would depend on how much she is making, how much you are making and what income or earnings there were during the marriage. There may be a good chance you wouldn't have to pay anything. This, incidentally, is one reason for trying to keep a good relationship with your ex...she may be agreeable to not even seeking any alimony.