[Wireless Networking] Can this be done?

May dad and his next door neighbor want to share a cable modem. Is it possible to have a wireless router in one house and get a "clean" signal in another. I hear of people stealing wireless but have never heard what quality of connection they get. If its not possible what is the maximum length a Cat5 Cable can be? For some reason I remember 100 meters.

100 meters per segment (you can connect segments with repeaters (hubs), though). How far apart are the houses? Chances are you wouldn't get that great a signal in the other house. I have a wireless router in my basement at home, and only get an ok signal on the second floor.

the houses are about 25 feet apart and the router distance would be 50 feet between PCs

You shouldn't have a problem with signal strength at that distance. If it hasn't been decided yet, go with wireless G. There will be less noticable signal drop-outs.