On a message board I frequent, someone mentioned they felt that a church-sponsored yard sale was unBiblical. A couple of other posters were confused, and didn't understand where that belief came from. While I'm not sure I would consider it *unBiblical* to have a sale at the church, I do think it would ill-advised.
My pastor growing up was very hesitant about allowing yard sales and such that were at the church property or otherwise "church-sponsored". He only allowed an annual sale as a *youth* fundraiser (and even that he wasn't thrilled about), with the proceeds going to the youth involved, and nothing to the church proper. My understanding is that he felt it was too close to the moneychangers at the temple, and it just looked bad to be using the church to make a profit for the church, no matter what good cause it would be used for - or ostensibly used for - which is the real issue. There is too much a chance of having - if not the reality of, then at least the appearance of - financial impropriety. However, if a group of members organized a sale on their own time and their own property, and donated the money to the church, he would have had no problem with it.
By and large, I do agree with his reasoning. Thankfully, this hasn't been an issue at our church, as far as I know, but I wonder how many other people would agree or disagree - or, most likely, just never considered the topic at all.