Start with the costs, not the listing
The seller's main out-of-pocket duty is the smog certification. California law requires you to give the buyer a valid smog certificate dated within 90 days before the transfer, and the whole county sits in the enhanced Smog Check program, so there is no lighter version of the test to shop for. If the car fails, the repair bill lands before any buyer can register it, which is why testing early beats testing the weekend a buyer appears.
The buyer's side carries the $15 base transfer fee and use tax based on the purchase price, and the buyer must report the transfer to the DMV within 10 days. One exception changes the math: gasoline, hybrid, and alternative-fuel vehicles 4 or fewer model years old skip the transfer inspection, and the buyer instead pays an $8 smog transfer fee. Knowing which side of that line your car sits on tells you whether to book a test at all.