@Patrick McBrian
Write your offer contingent on them delivering the property vacant. Your Realtor should be communicating with the listing agent to find out what sort of timeframe they need to complete the eviction process. Don’t close until you verify the property is vacant. CA purchase agreement gives you the right to do a property verification walkthrough in the last 5 days before closing. If on your walkthrough, you find it’s still occupied, don’t allow Title to close the transaction.
If the sellers insist on you making this your problem for the price they are offering, you need to talk to your lender and attorney to fully understand what happens if they end up staying more than 60 days past closing.
Another option is to offer to pay cash for keys or even credit the seller an amount for them to do that before closing. We have seen some astronomical numbers paid to get tenants to leave in CA but you never know how much it will be until you try.