We're not fulltimers, YET, but would like to make a couple of suggestions.
Try to find a rig with 15K air conditioners, WITH heat pump feature. The 13.5 units have a hard time keeping up in really hot weather!
Double-pane windows would be a MUST!
Tinting on the windows would be great, the darker the better to keep out that southern heat! Of course you can add this to any rig.
Awnings over the windows help.
Good luck, happy trails, and God bless!
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Joe & Annette
Sometimes I sits and thinks, sometimes I just sits.....
2002 Monaco Windsor 40PBT, 2013 Honda CRV AWD