There are a few things to note about trailers and tow vehicles before you learn the hard way. A 20' enclosed is about the limit for an ordinary truck, like a Tahoe or F150 or the like. Anything higher and the trailer will cycle on you. A 20 foot is nice but is harder to resell because there is no extra room once you add the car, spares, toolbox, etc. If you ever want to expand and add shelves or cabinets, you'll need at least a 24'. And to tow 24 feet or above for any length of time with little stress will take a dually. I know a suburban or really big SUV can handle the trailer, but the dual wheels really make a big difference. Especially when you start adding more weight to the trailer with all the extra unnecessary junk you will throw in it. Its like a house, the bigger it is, the more stuff you will throw in it. And the more weight you add, the more dangerous it is to tow.
So, it really comes down to a regular truck with a really good open trailer or step up to the 24' plus. I've towed an E36 BMW in my 20 foot and there was very little room to spare. The car and the tie downs took up the space where I would have put my tool box and spares boxes. And the trailer snaked all over the road. This was with a Tahoe/Pace Shadow combination that gave me very little trouble when towing a lighter/smaller car with all tools and spares.
I'm in the process of buying a new trailer/tow vehicle combination and its either going to be a 24' gooseneck with a Chevy 454 dually or a 1500 with an open trailer.
