Last year I spent a ton of time thinking about how to have my current trailer built. I just bought an open trailer last year and ended up having it custom built, so I really thought a lot about what should go on a trailer. A lot of the same concepts can apply to an enclosed trailer that you are looking at. I actually almost decided to go with an enclosed, but the enclosed I priced out was going to run me $6000-$7000 by the time I had all the options installed on it that I would have wanted. Look at what dealers you have around you. I know some people don't mind traveling to buy a trailer but if you don't have a dealer for that trailer nearby, it may be difficult to get warranty work done or get new parts quickly. Haulmark, Wells Cargo and Pace are some of the big names in the enclosed trailer industry, but like I said you also have to consider what dealers are in your area. A few options that I would suggest would be teh extended tongue, upgraded 5200lb axles, extra lights inside, LED light package, side vents and/or roof vents, extra height package, spare tire, and a stone guard on the front. I would also suggest a trailer tongue box if you can get one mounted. Some people really like having a cabinet or some type of shelving in the trailer to help keep things organized and be able to carry their extra 2-cycle oil, trimmer string and some tools. Sizing an enclosed trailer is a little different than an open trailer. I always suggest getting a larger enclosed trailer than open. For example, if a 83"x16' open trailer would be big enough, then an 8.5'x18' enclosed trailer would be a comparable size. Space always fills up fast as I'm sure you know. You do want to make sure that the trailer you get has quality materials. The wood used for the floor and sidewalls should be thick enough. The 3/8" sidewalls and 3/4" floor should be pretty much standard. A one piece roof is also a must to avoid leaks. Studs/support posts should be 16" apart. I know that enclosed trailers can have problems with leaking at seams, so it may not be a bad idea to take some chaulk yourself and make sure everything is sealed up nicely. You will want to make sure that your truck will tow it nicely, it is going to be like a sail behind you so you'll get a ton more drag. I wouldn't worry about a CDL, you shouldn't be over the limit unless you are towing it with a very large truck (like an F450/F550). Make sure that you explore all your options and look through a trailer well before buying. Since it is a fairly big investment, you'll want to make sure it lasts for quite a while.