Does your buyer wear a black pork pie hat and call himself Herr Heisenberg?
Do be aware that since Swiss banks have begun to distance themselves from dodgy assets reports of money laundering via Swiss real estate seem to crop up more often. Are these stories true? Who knows. But as you don't want to lose your money by becoming an unwitting accomplice, eyes wide open.
The first thing you should do is to speak with your bank manager about the transaction. He/she should be able to discuss compliance concerns.
In addition to caution money laundering, to be on the safe side you probably should also consider counterfeiting.
If you choose to go through with this, you and the buyer with his briefcase full of purple Chuffs should meet at your bank. Each note should be examined and authenticated. Then put into an escrow account.
When KYC and counterfeiting concerns have been put to rest then you proceed with the sale.
Yes, many Swiss still think nothing of paying cash for big ticket items. But pulling the price of a house out of the mattress raises eyebrows today, even in Switzerland.