I would look for screws that are beyond just rusty. When I stated pulling the trim off the skirts of my Lance 845, some of the screws were without threads, others were about half the original length. Since I always have a Swiss army knife in my pocket, it is easy to pop a screw in and out to look at it. Have never asked, just have done it. Try to remember the ones you take out for it you buy it, you need to put a touch of caulk in the screw hole and run it back in.
You can have rusty screws and not have any damage I have found. The quality of the screws used on most RVs, matches the quality of the workmanship in many cases. Just not the best available. I tend to replace steel screws on my RVs with a good grade of stainless ones and caulk each hole before putting in the new screw.
Around an area of high humidity, like here in south Florida, (I live 3 blocks from the ocean) steel screws/bolts, etc. will rust in the original box on a shelf in my garage. I keep most of that stuff in sealed Tupperware type containers. So to find surface rust on a RV here in Florida, I would expect it and not be too surprised, now screw deterioration is different and would indicate a water leak. A potential buyer has to figure the cost of time and materials on buying any RV that needs work. We have some forum members that could buy the damaged TC Bob has posted the photo of, and six months later, they would have it looking better than new. If a person has the time, the talent, the tools, the space, the money and the interest to do the work themselves, there are lots of good buys out there. The labor cost to fix the one in Bob's photo would be out of sight, but as a hobby project, it could be good for some people at the right price.
Also rely heavily on the smell of the unit. Wood rot, mold, etc have a distinctive smell. While my sense of smell is about dead, my wife can spot a molding smell every time. Maybe I should train my beagle dog to spot and respond to rotten wood. He could become a paid shopping consultant. (with me as his agent, of course. LOL)
joe b.
Stuart Florida
Formerly of Colorado and Alaska
2016 Fleetwood Flair 31 B Class A w/bunks
www.picturetrail.com/jbpacooper
Alaska-Colorado and other Trips posted
"Without challenge, adventure is impossible".