Assuming you wanna haul lots of tanks and stuff, I'd highly suggest getting one with a heavier axel than you think you'll need. I'm assuming you're looking for a 6x10 foot Haulmark style. Go ahead and get a 3500 pound axel instead of a 2,000 pound one. Once you get tanks, coolers, etc, maybe a BBQ grill it'll get heavy and you want the extra axel. Also get heavier duty tires. One thing that trailer companies do is buy "old" tires from tire stores that only have a 5,000 miles or so left on them in order to keep costs down and be competitive. If you're hauling a lot of weight, you'll want new tires as they are stronger, etc. (Old tires can easily dry rot quicker).
Also consider crank-down jack-stands on the rear of the trailer. That way you can walk into it when it's not hooked to the trailer hitch of your town vehicle without it "tipping" backwards. A real nice feature, especially for loading in the garage the night before.....
A front "side door" is also a nice feature to getting to stuff in the front. Also consider adding bright reflective strips on the back as trailer lights don't always work like they are supposed to. Also pay the extra to get the LED trailer lights. Much brighter and less prone to failure.
One last thing.... A friend put slotted track in the floor of his trailer and then plywood the same thickness (of the tracks) on either sides (of the tracks). This way he had a flat/flush trailer bed but tie-down points in the floor to secure large loads such as his motorcycles.
Whatever you do, it's always nice to have the ability to use it for other stuff, so being able to remove any racks or mounts easily is a nice thing. Or install them on removeable mounts.
Hope that helps.
Mike
