Though Joseph, the father of Jesus, was prominent in the bible, not much is known about him. He was a carpenter, and the church designated him the patron saint of workers. Beyond that, there really isn't a credible source for the current belief that the burial of his statue in the yard of a home will hasten its sale.
Generally, it's believed that the seller should bury a statue of St. Joseph upside down and facing away from the home. From there, exactly where to place the statue is open to interpretation. Some say it should be near the for sale sign, while there are proponents for just about any location in the yard of the home. The general belief is that, once the home is sold, the statue should be exhumed and placed in a position of honor in the sellers' new home.
This practice has become popular enough to spawn companies that sell St. Joseph kits for home sellers. For as little as under $5.00, a statue and burial bag can be purchased to help the sale of a home. If you're about to advise hiring a home stager, maybe this isn't such a bad investment. Sometimes just positive expectations are said to bring positive results.