Building a cart?

How hard is this to do? Has anyone done it themselves?

More info: I'd like to build a small, 4 wheeled cart. I was thinking that getting something like this:

But bigger, then modifying it would be the easiest and cheapest way to do it.

I'd really like something like this:
But I don't have $17,00 to spend, and I don't need anything that fancy. But the basic idea of a flat sort of cart is what I want.

I would recommend trying to find a used one. You will end up with a lot of expense into making one by the time you get all of the hardware and wood. I also don't recomend trying to convert something that was not intended for horses. The type of wagon to look for would be a buckboard. They are usually flat behind the seat.

your better off buying a used one.

Since you're willing to do the work, maybe a good bargain would be a used wagon that needs some work. That way you don't have to start from scratch.

My Dad and I are in the prossess of building a 4 wheel marathon cart, but Dad has alot of knowledge in all kinds of things. We are going to build the frame out of square steel tubing, and put either expanded metal or aluminum on the parts that should be solid looking. Hydrolic brakes front and back, fifth wheel with brake, etc, etc.