Re:Custom Made Fiberglass Concession (HELP)
First I hope your dream comes true, and wish you the best but vending is not a get rich quick operation. It involves long hours, working in what ever the weather brings and many disappointments along with some rewards.
That said and mark my words, "DON"T LOOK FOR A BIG EVENT WITH NO EXPERIENCE." Do a dozen or so small fest then you'll know what your doing right and what you need to change. Even if you have some restaurant experience, (which you didn't mention) you'll find vending is an entirely new ballgame. Start small and work your way up, it'll pay in the long run.
Now as to a custom made unit, again and sorry, (not good news), I'd strongly consider finding a used trailer and work it for awhile before I spent a ton on a custom made operation. You may not like this business and all the work and stress involved, lots of people don't and that's why there are so many used trailers and for that mater so much used restaurant equipment for sale across the country. And the used equipment (including trailers) can be bought for pennies on the dollar if you shop carefully.
Best of luck