Look at jig saws, bandsaws(wood working ones with a metal blade) pneumatic nibblers, plasma cutters. All can be had cheaply on Craig's list, Ebay, Hrbor Freight, or manufactures repair houses(Dewalt etc.). Multiple links here on how to.
https://www.youtube.com/watch?v=dusN8HcwGWg
Bill
https://www.youtube.com/watch?v=dusN8HcwGWg
Bill