Well, you can't legally pull any passengers in the trailer. It is only for show or to haul things in.
I do civil engineering where I work and we are also a steel fabrication shop, so if I added up all the time spent in fabricating, steel stock, painting, etc... it would be such a high amount that no one would make this trailer. I paid cost only on materials. No labor charge for anything. With just steel materials, hitch, jack, and paint I have about $250 in that.
First you have to start with a complete car. I bought that champane '95 Contour for $150 and sold/scrapped parts off of it. The car was basically free in the end. You will not get that lucky and will probably spend around $500 for a complete car to cut in half.
Then you need the body kit. Rear bumper and mesh I did some trades for. The side skirts I traded/got free a damaged left and right skirt and cut them down to the length I needed. Filled in the ends that were cut, added brackets to hang the skirts. You will most definetly have to buy these parts from people and you could be spending up to $400 for those parts if you don't buy an actual SVT Contour to use the parts from.
Interior parts I had here from previous cars I parted out, so those were free.
The 2 extra wheels I had here from a car I parted out. They were basically free too but you could see up to $300 for 2 wheels and tires.
The springs, one side had 2 coils broke off so I just cut 2 coils off the other side for an even looking drop.
The exhaust tips are generic 3.5" double walled angle cut. I think they were about $30 and I had to make a custom bracket to hold them in position......
So really, what my cost was and multiply that by 5 and that will give you a good idea on how much it will cost you. PLUS you still have to factor in all your time to do it. Remember, I work at a steel shop and we had every machine and all materials on hand.