WOAH, you can't do that with melamine, it costs around 25 bucks for a 4 x 8 sheet here. MDF is around 20 bucks, so you would end up with a smaller rack then you wanted.

You could try plywood as long as you coat it with polyurthane. That's what I'm going to do and its only going to cost me around 30 bucks. And then, in a year or two, I'll go for a plastic rack....

EDIT: also, my rack is going to hold 6 snakes, and it's going to be 42" tall, and 38" wide... 5' x 4' is gonna hold ALOT of snakes...lol.