On Networking Two (Or More) Houses?

An Anonymous Coward offered this curious query: "A friend of mine lives four houses down from me. Of course, we're both flaming geeks, and have gotten it into our heads to network our computers over this distance. We've tossed around a few ideas, such as a few of the available wireless kits, or stringing up Cat-5 along with the phone lines. The problem is, we haven't found anything that can send a signal far enough, or else the process of connecting our houses together with wire would surely leave us electrocuted, and in jail. Anyone know of something that might work?" Interesting thought. Shaking my Magic 8-ball for an answer, it responds: "Possible, but solution may be expensive."