Per CA FTB Publication 1031:
"When you are in California for other than a temporary or transitory purpose, you are a California resident."
https://www.ftb.ca.gov/forms/2021/2021-1031-publication.pdf
You may also want to read Change of Domicile on page 10 of that reference.
If you have constructive receipt of the proceeds from your home sale after you become a CA resident, then they are taxable by California. Constructive receipt of income is a tax term which determines when a cash-basis taxpayer has received income. Constructive receipt of income occurs when a party obtains income that is not yet physically received but has been credited to the taxpayer's account and over which they have immediate control.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
