Legal Question in Credit and Debt Law in California

If the house is sold at an auction there may be other bidders and the cost of buying the house may be higher than the amount of the debts.

If you can buy the house before the redemption period expires, yes, in theory you could offer him a purchase price slightly above the amount of the debt, with an escrow that requires the debts be paid and cleared, and any additional funds left go to the current owner/seller. However due to massive abuse during the housing bust, such transactions are now highly regulated and violations can result in penalties ranging from reversing the transaction, to judgments requiring you to pay the fair market value, to fines and even jail time in extreme cases. So do NOT go into a transaction like that without solid legal advice.