Buying our first camper and have a AC question

If I wanted the trailer, ? I would buy it - if the ac is to small are not efficient, replace it with a bigger unit. Rule of thumb is 5000 ac god for say 96 to 100 sq ft. But in an RV is much different than in a house. In the 12 foot I am building now, I plan to use a 5000 btu, in the back end, with a helper fan, however the walls and roof are better insulated than those you buy. Good luck with your new rig.