What a vehicle can pull and the true payload available for loaded pin weight and cargo in the trailer are two different things. Search the forum and you'll find many threads with lots of detail on this topic. With almost any 1/2 or 3/4 ton vehicle, you will hit the limit on payload (read tongue weight, people, fuel and gear) long before you hit the maximum towing capacity. When making calculations, use the gross weight rating of the trailer off the sticker rather than empty or published weights.
After that, on a used trailer your main concerns should be tires, wheel bearings and water integrity (roof, leaks, previous water damage, etc.).
Rob
U.S. Army retired
2020 Solitude 310GK-R
MORryde IS, disc brakes, solar, DP windows
(Previously in a Reflection 337RLS)
2012 F350 CC DRW Lariat 6.7
Full-time since 8/2015