In CA, a termite inspection is required, and you should have gotten a termite report before you completed the sale...with enough time to approve or disapprove of it. Decks may or may not have to be inspected...this is an issue in many sales. If the seller knew the deck was damaged, he or she should have disclosed that information whether or not the deck was officially inspected.
If the deal is not completed, you can most certainly ask for repairs or cash to make your own repairs. Whether the seller agrees is another matter. In a home sale, nearly everything is negotiable. The issue for you is whether or not the home is such a deal that you are willing to take it on even with termite damage to the decks.
If the deal has been closed, you might want to explore legal remedies if the amount of the damage is significant and if you are sure that the owner knew about the damage and did not disclose it. If you're looking at a couple of hundred dollars, it's probably not worth the hassle and legal expense. For $1000, maybe a lawyer letter would net you some compensation and be worth looking into. It is illegal to NOT disclose material facts about the residence if you are the seller (or, if you are the agent and knew about the issue).
Good luck with this!