Since you are a newbie. You've heard all the weight stuff already. Think also about the features and tech stuff.
1. Water heater both AC and propane. My newbie neighbor got propane only and has to listen to a propane burner even when he's on 120 AC.
2. Get lube-able axle bearings. (Super lube or easy lube).
3. Make sure it holds enough fresh, gray, black water for your use needs. Many bunkhouse models have smaller tanks to get extra bunk space. I owned one once like that.
4. A better suspension thats better than just a standard equalizer keeps the rig from jumping down the highway.
5. Dont get carpeting. The new simulated wood looking floors hold up much better.
6. IMHO Almost all trailer tires are a load range lower than they really should be. Example -- if they are C rated, should be D rated.
There are lots of other issues. Think it through. Dont be bulled by a sales rep.
