Well, you have a few options.
1. Purchase a copy of Retail and host a server. Any other computers on your network will be able to play LAN.
2. Run hundreds of miles of networking cable from your home to your destination computer.
3. Similar to two, but more reasonable, if you live next door to someone you want to play with, you should be able to run a temporary cable out your window and into your neighbors house.
4. Similar to three, if you are stealing the Internet from your neighbor with a wireless connection, you will be able to play LAN with them.