Water damage. That can destroy any value in a travel trailer, and can happen in any TT that has been through even one rainy season if its been outside and not properly maintained, even if its never been camped in. Sometimes its hard to find, look for rippled or stained walls but also carefully inspect the floor all the way to the outside walls all the way around, Look for softness and lifted flooring. Moldy smells. Look underneath especially at the wall to floor connection. Any sagging or dampness?
Bent frame or axle from rough use or overloading. Also could be present in any TT that isn't right off the lot. Ask the seller where he has been camping. If he had taken it on a lot or rough forest service roads it might be better to look elsewhere, rPods aren't well suited to rough road use.
Look at the wheels from behind the trailer. Are the tops of the wheels bent inward (called negative camber)? Uneven tire wear? Park the trailer on a completely flat spot. Does it lean to one side? is the bottom edge of the trailer cabin the same height above ground on both sides (within half an inch or so)? Look at the trailer from the sides. Is the frame straight from the tongue all the way to the rear bumper?
Other than that, the most expensive thing age related item that you could run into would be replacing the fridge. RV fridges have a limited life, figure on replacement every 10 years or so, and they cost north of $1K,
Have the seller run all the appliances and equipment for you, if it all works then it might nickel and dime you later but shouldn't break the bank.
Did I mention water damage?