I have to disagree with some of the comments.
For one, the server software is free. You can download the apache web server at
http://apache.org and install it on windows or linux, not sure if the have mac.
It is not hard at all to run servers from home, I actually have a bunch with several hundred websites. But I have a commercial accountwith 1meg of bandwidth and dedicated ips. That costs me $150 a month.
But I must add, I run a hosting company and I do server administration and run servers in a datacenter that run dns and client websites. For me, the home network offers floor space that is too costly in the datacenter. Also, the convience of having servers within an arms reach is great when developing applications that require hardware adjustments or additional networking components.
If you are not an expert, then you will most likely have a very insecure and poor performing server. The cost will be high if you have any bandwidth and it will cost you for power and heat up your home.
If you have 100 websites, the cost savings are big. If you have one or 2 websites, it will be very expensive per site to run from home. Much cheaper to buy space from a commercial host.
You still need 2 name servers and a web server, at least 3 ip's and at least a 256k upload which might manage 4 similtaneous connections at best.
You would not be happy with the results and you are not a system administrator monitoring the server activity and patching security holes.
As I said I have a commercial account and I would say in the last 8 months I have been down more than 48 hours due to network issue with my isp. Compared to my datacenter with 0 downtime.
But if you want to play, I highly recomend it.
The market is constantly changing and more and more bandwidth is becoming available. I think in 5 to 10 years many people will be running their servers from home of offices rather than paying datacenters.
It will definetly open doors for you that you don't have with a leased server and you will learn much about managing websites and servers. I have developed applications at home that I could never have done in my data center because of the cost of space and bandwidth.