You didn't say what model of Class B. Pay particular attention to the upfit components, which will probably not be as well-protected as the chassis. Our rig appeared to have spent much of its life in Ohio prior to being moved by us into Texas. I've had to do rehab work on a number of its embellishments; for instance, this blog post
describes a POR-15 job I did on the ground effects support system (running boards and associated wheel trims that run from stem to stern). I also POR-15'd part of the exhaust system, even though POR-15 is not warranted to withstand some of those temperatures (it discolors but seems to be fine).
The potentially good news is, although you may have to deal with more rust, you should have less rot. Northern vehicles age primarily by rusting. Southern vehicles age primarily by rotting. We have a friend who owns our same Class B model and year (met him and his wife on the forums), except his has lived its entire life in Texas. His is almost rust-free, but every belt, hose, connector, and other rubber- or plastic-based part has basically failed by now or is just about to, even big heavy parts such as the turbo-charger hose (diesel) that in more benign environments might last close to the life of the vehicle, but in his case, it spontaneously split (so did his propane fill line - bad situation there). We don't have that particular problem with our rig. Not yet, anyway.