It is possible to turn your computer into a host. You'll need to go to www.php.net and download php install it (which is free) and when you install it near the end of the installation it will ask you what kind of server you want to set-up. Generally a lot of hosting services use Apache, you may want to look up the other selections allowed. It shouldn't cost you anything, other then time, patience, and maybe a computer if you get to frustrated.
I myself don't know too much more on the subject other then that. I also would think it could be hazardous to your computer, being that it is directly connected to the net 24-7 running it's server, and database. As I said I would think, I'm not sure.
But another alternative would be to get a good free-host which supports MySQL, as well as PHP, and just simply get a shortened url. I myself use to use
http://www.freedomain.co.nr/ which would allow you to get turn "www.
YourFreeServer.com/
YourSiteName" into "www.
YourSiteName.co.nr". There are other shorturls providers on the web you just have to find them.
Another alternative to for that site for your friends without using your own server, and a free server, some people (generally) bloggers who purchase a domain, as well as a host, have so much space with their package they don't know what to do with it all, literally. Sometimes they will have a sub hosting service, this way they help out someone else in need, and also get some use out of what they are paying for. If you want this option let me know and I'll send you some links i know of. Generally they will want you us a FTP you can buy an ftp program, but there are some free ones with the GPL license. For instance like filezilla.
Hope it all helped. if you have any questions personal message me.
Later,
Ben