Hi -- He could sell it for what he likes or indeed give it away, but gifting or the sale of a house undervalue to avoid stamp duty and possible care home fees will always attract attention from the authorities, and the whole process can be voided and overturned if they believe you have intentionally "deprived yourself of capital" in order to evade impending care home fees or to evade stamp duty.
He needs to see a Solicitor who can better advise.... once his current needs & circumstances are fully known, there are ways of doing this including placing the property in trust if it's beneficial.