It's not, or didn't use to be, all that unusual in houses. It's referred to as building "on spec", meaning "speculative"; where the architect, builder, or whoever builds the house on the chance that they can make a profit selling it after, rather than the more common way of building it to an up-front contract. It was most often used when a builder had materials or a little cash available to avoid laying off good workers when there wasn't a contract job available.