自住房加孩子没事，出租房加孩子要变tax

https://www.boe.ca.gov/proptaxes/faqs/changeinownership.htm

see answer 2 and 3.  

1. Any change of ownership bertween spouse is excluded.

2.  Changes of ownership betweeen parent/child of primary residence is excluded

3.  But I think rental property between parent/child is not and should not be excluded. 

The reassessment is not the whole property, but for the portion of property that changed ownership.  For example, if dad and mom owns the rental, and added a child, 33% of the interest is transferred therefore 33% of the property will be reassessed.   If owner is only dad and you added 2 children's name, 66% of the interest is transferred therefore 66% of the property will be reassessed.