Network Configuration using a router?

I want to setup a small business LAN to share access to each other and to the internet over DSL.
I read that it is posible to setup a LAN using a router with DHCP support. This is exactly what I want to do for now. I am not looking to spend money on anothercomputer to host a network. Can anyone give me suggestions on how to configure this setup and/or links tsome helpful networking site that might deal directly with this type of LAN configuration.
BTW, this network will consist of at least 15 computers (all Desktops) that will share internet access and access to an inventory system...any suggestions would be helpful.