Please see post 54. I cannot recommend a router strongly enough. The benefits mean that you can connect 4 PC's to a single cable/DSL modem and pay the single PC cost. Or, you can daisy-chain even cheaper switches together and connect over 250 PC together. You will be inheretly immune from most virus attacks, as the Router's built-in (and automatically enabled) firewall will protect you.
Other pluses, the Router will serve as a firewall between the hackers and you. There are a gazillionty different combinations of codes to make it through the router to your PC. The router randomly re-assigns these numbers to each of your home PC's every hour, day, week (you set that up). It blocks ports that you neither want, nor need open. It's easily configured (literally takes you all of 10 minutes - yes, even a novice).
Cost is low. I mean, you can find a Router for less than ~$50 pretty easily.