videotape your pdi. have them demonstrate and you return the demo on everything. If it opens, closes, moves, turns on or off then are sure they operate it in front of you and it functions properly. Run slides in and out. Have them open up the water heater compartment and show you where the water heater and water pump are. Have them show you how to winterized and dewinterize the trailer. have them locate your low point drains as well. Check all caulking, climb on the roof and inspect it for bubbles and cracks. look in and around the trailer for signs of leaks. Do not hand over any money until the pdi has been completed to your satisfaction and any repairs completed to your satisfaction. Be prepared to leave the trailer there for a bit if repairs are necessary.
The things we found within the first year on our zinger were: the dinette drawers needed to be realigned (found on pdi) , the slide rubbed a hole in the carpet (replaced under warranty and no issue since), and a couple other small things I can't remember.
Enjoy your new zinger!