It's not actually against any rules that I know of for a priesthood holder to preside over the sacrament at home or in a small group, or even for himself. I can really only speak for how things are done here in Utah where there are such a large number of LDS families living in close proximity to one another and to a ward meetinghouse, but typically here, a couple of priesthood holders will take the sacrament to the homes of house-bound individuals who would not be able to receive it otherwise. Perhaps in parts of the world where this would be very inconvenient, it's not done as much. Other than to say that the sacrament does not have to be prepared or passed within the confines of an actual church building, I'm going to let one of the "guys" (i.e. priesthood holders) answer this, as they may have discussed the rules in Priesthood Meeting and know something I don't.