What does smith mean when he says our lodgings castles in the air?

The phrase "castles in the air" is a metaphor used to describe something that is imaginary or unrealistic. When Smith says that our lodgings are castles in the air, he is suggesting that our expectations for our living arrangements are too high and unrealistic. He is saying that we should not expect to live in luxurious or extravagant housing, but rather in simple and practical lodgings that are suitable for our needs.