Buildings in CryptoVillages are owned by the player in-game and are linked to them through their MetaMask address. That means, unless otherwise sold on the marketplace, all buildings owned by any given player are locked to that person's wallet and inaccessible by anyone else. Any upgrades the building undergoes are retained permanently, even after being sold to another player!
There are 11 different building types players can own within CryptoVillages. These belong to one of three categories based on how they were obtained: Standard; Premium; Stakeholder; and Castles.