The owner is allowed to keep a key only if the tenant is allowing him. You can change all the locks as tenant if you do not allow him and if you are not sure he

The owner is allowed to keep a key only if the tenant is allowing him. You can change all the locks as tenant if you do not allow him and if you are not sure he is not keeping a key. If your contract stipulates that you must leave the owner a key, you can still change the lock, the clause in the contract is by law not valid.