A few thoughts...Tires...if the original owner covered the tires
they should be fine. Age is always a concern as UV damage compounds over time. If they were covered they should be fine...inspect for cracks in rubber side walls and between the threads. I'm not a fan of what some call EZ Lube fittings as it is too easy to pump lube greese into the brakes
The brakes: use your controller to test the brakes the first time you roll. You might hear some squeaking as any surface rust is scuffed off the drums.
After purchasing any used trailer have it inspected (tires, bearings, and brakes) at an RV dealership. I suggest an RV dealership because all too often the local auto repair shop uses the wrong parts. Best example of this is using the wrong wheel bearing seals and that caused you to leak bearing greese (not a good thing). Because your unit has had little use and is almost new the other items like appliances, water heater, air conditioner and water pump should be fine (I assume you tested them prior to purchase).
Good Luck and Happy Camping.