Don't depend on the dealer to check it out. Have them show you that everything is working - hook it up to power, run the AC, the heat, tell them that when you come, you want to open the fridge and freezer to feel the temp, check for obvious signs of water penetration. Check to make sure you have hot water and good pressure. Look under the cabinets to be sure there are no drips. Then get up on the roof and inspect the roof. Don't expect it to be pure white, but it should be in good condition - and check the caulking for cracks. If you see cracks, then it needs to be redone - most likely needs it anyway. Inspect caulking around the exterior - especially the door and windows.
If they don't want to accommodate any of this, then walk away. Good luck.
