Backing up about 50 computers

I was literally thrown into my IT postion. I am a newb. I know some but not enough for what my position is so I’m asking for help :). I am the ONLY IT person in my company and have about 60-75 computers. What is the best way to backup all of these computers? We will be moving buildings in about 6 months and I will be responsible for moving the computers, servers and phone lines. (yippee) On top of that it has to be done cheap very very cheap.. In my experience you can’t seem to move 3 computers without one of them getting messed up some how so I am trying to backup everyones computer just in case of failure after the move. Any suggestions? (less than 1/4 of them actually have cd burners.. and are over 4 years old.)