Wait I totally forgot, there is a way to share your Mouse/KB with software for free!
http://www.inputdirector.com/
I have used it at work before and it worked well, it was sometimes buggy and I had to set a firewall rule for it, but once setup it worked great. It actually lets you use two different machines, but two different monitors as if they are one, so you can drag your mouse from one to another. Very cool