Like others have said, get more than you need. You will use it later. A 6x12 would leave you room for ice chests, corn, etc.
Tandems are great, but if you need to move it around by hand single axle is nice.
I bought a new 6.5x12 with gate here in Houston a couple years ago. I gave around $900 for it if I recall correctly. TSC is high on trailers.
I spec'd mine with EZ lube axle and bulldog hitch. Tongue runs all the way to the fenders, and is made from 4" channel. Cheaper models will have 3" and only go to the front of the trailer.
This. I haul my Teryx4 on a 16 foot tandem. It has a job box on the front and I have room for the ScS and coolers. It tows great, never know it's back there. I would not want to tow these things on a single axle trailer. They catch a lot of wind, which results in trailers walking behind vehicles.
If I could redo it, I would have a 20 foot car hauler. Makes loading stands much easier, tying things down is easier, and I can still have rails up front to keep coolers from sliding off.