Also, sometimes it's not worth putting really old computers on LANs, because you need to buy special equipment for them, or the networking software takes up too much disk space and memory. Sometimes it's difficult to tell, because the slot of a modem phone line is very similar to the slot for a 10-Base T cable. If you are running a 10-Base T network, you will also need at least one hub. Windows 95, you will need a network software. Networking hardware is made by many companies.
Cost definitely translates into quality on network hardware.
3-Com sells a useful package called Office Connect which includes everything you need to connect three PC clones together. However, you can also buy everything piece by piece. You need to have software on each machine to allow them to be able to speak the same language to each other. If all you machines use the same operating system this is pretty easy. The cheapest way to buy the equipment is often through mail order places.