I am thinking of making a webhosting service. I will have a free and paid service. I want, however, to host it all on my own server. I was wondering, does anyone know where I can find a fairly cheep computer that will function as a server? I have the high-speed ISP already, and a router for my connection. I just need the computer. Thanks in advance.

Make sure you check with your ISP before you start hosting sites. It's not likely that they'll want you offering hosting to others. Some don't even want you hosting a personal site, and they'll check the HTTP port (80) to make sure that you aren't.

This is a transcript of a chat with my ISP

innocentkiller> hello
Analyst> Hello and thank you for choosing Comcast. My name is Patricia and how may I help you today?
innocentkiller> Is it alright for me to have a domain and have it point to my IP address. I am thinking of opening a webhosting company, and want it on my own personal server. Is this ok?
Analyst> I do apologize but Comacst does not suport the web domains.
Analyst> You will have to do it yourself, you can but we do not support any part of it.,
innocentkiller> So does that mean that port 80 is blocked?
Analyst> Comcast does not block any ports.
innocentkiller> ok, thank you.

This is confusing. Does it seem like they will or will not allow me to do this?

It sounds like you are allowed.

Make sure you do all the necessary research. There is a lot more to running a hosting company then just hooking a computer up to the cable.