I bought my FF x-139 after it had sustained water damage. You can tell it when you touch the walls...the luan paneling should feel rigid when you slightly push on it...if it has been compromised by water it will give and feel spongy. Look in the corners for small traces of mildew, especially on the wallpaper borders to see if the paper is smeary. Look carefully around and in the celing light fixtures for sign of dried water drips...usually brownish.
If the roof has had water you will see small lumps...I haven't figured out what those lumps are...something from the de-laminating or the foam filler...not a problem if you seal it up, will just add some "texture" to your decor!!!
If it was caught early and didn't do extensive damage, you can get a bargain. But you need to get up on top and seal it immediately...don't assume someone else did it right. Also re-caulk down the exterior corner mmoldings...a litttle crack will let in water. And another good way to be sure is to take off the air-conditioner shroud and look around for damage...seal up the edges with Eternabond tape and it'll be good for years!
If you get there and the damage was extensive, bargain it down!
Oh and don't forget to come back and let us hear how i went!
Susan in VA
2005 Sun Cruiser Fun Finder X-139FK
2000 Jeep Cherokee 4.0L (Winston)
Cadillac Sedan de Ville V8 (Great White Whale)