This is a very long distance for a network . You can't use normal UTP CAT5 cable because after 100 m it needs devices to repeat the signal. You can use a dial up connection or ISDN using a phone line but your network will not be really a network because you'll access your grandfather computer through the internet.

For such a long distance you should use fiber optics cable. Your network connection will be at a very high speed but it will be very expensive.