I've never actually used WHS so I can't comment on it too much, but I can tell you that it has been discontinued. I would imagine that support will continue for some time but, if I'm not mistaken, you can only buy WHS preinstalled on hardware, not just as software to install yourself, so it may be a bit harder to find now. It's designed to run headless, i.e. management is done via remote connection, so installing yourself might be tricky.

There is a new version of Windows Server in the 2012 range called Foundation and that is the new basic model. More expensive than WHS but more like a regular business server.

If you don't need to run Windows-specific software then you could always use Linux, which would cut the software cost to essentially nothing. You certainly wouldn't have an issue installing MySQL and there would be tons of information on the web about running MySQL on Linux.