It all has to do with the amount of metal work you plan to do in your life. If it is a lot, start buying punches, breaks, shears and welders. If you are only going to do one chassis once in a while, draw it in Autocad or illustrator and take it a metal fab shop. You would be very surprised to find out how much the second one with the exact specs cost.
It is the first one where all the cost is. I was a metal worker as a career in my younger days and have acquired lots of tools and still have access to metal fab equipent, but still will pay for one chassis if that is all I need.
HBP's suggestions were great for cutting holes. A good place to start is buying punches in the most common sizes, but you would be surprised to find out what you can make in most available prepunched chassis and mort are less than 1 punch.
If I did not already have the metal working equipment I have, I would never buy anything other than step bits, nibbler, nice saws and files and of course a nice corded 1/2 drill and corded 3/8 to go along with my cordless. Oh yea, great drill bits in a complete box with triplicate of all the ones 1/8the and smaller.
For instance, I have a TIG welder I use once every year maybe. Doesn't make sense to even have it or the argon bottle.