Control two or more computers at the same time with one keyboard and mouse

Control two or more computers at the same time with one keyboard and mouse I have 5 systems, I need to access all systems same time. If I click start button from 1st system, automatically open start menu on 4 systems. If I open notepad and type something this process also done remain systems at same time. Can anyone give me a solution. I am ready to pay 10$ for right solution. Thanks.