Jimmy Akin blogs a question from a reader about burying a St. Joseph statue upside down in your yard to sell your house. Yes indeed, this is a superstitious practice, and not something I condone (although I heartily recommend asking St. Joseph for his prayers if you're trying to sell). Nevertheless, I worked in a Catholic gift/bookstore once, and one item which we could not stock enough of was a St. Joseph home-sale kit. Fortunately, the package clearly stated that the superstitious practice was wrong and the prayer should be done out of devotion. I know superstitions are not spiritually healthy, but every time we sold one, I hoped that Joseph would also pray for a continuing conversion of the purchaser.
Oh, I just rechecked Jimmy's blog, and it looks like there is a debate over whether this is a superstitious practice or not. Folks, it is. There's no way to get around it. An individual might not understand that it's superstitious, and may do it out of pious devotion, but it's still superstitious and it would be far better to practice a more traditional devotion (praying a novena, lighting a candle, consecrating your firstborn to the priesthood, slaughtering goats) in petition for your intention.
I seriously had never heard of this until you brought it up a while ago. Maybe it's my inner Protestant talking, but such a practice seems to me to be so weird. (And I have gotten better about some of the stranger Catholic practices-- I can now look at the Sacred Heart of Jesus images without thinking of popping blood vessels, gushing blood, and overall cardiovascular failure. :) )
I would also think that such a practice seems insulting-- I guess some people would like it if their statue were to be buried upside down, but if someone did that to a statue of me, I'd make a pouty face and exclaim, offended, "Hey! You got my statue all dirty!" :/