@WCBlueSky :Those two photos don't show any real rust. Rear axle is out of focus but if that's rust it's just surface.
Places to check for (real) rust:
Under the rear hatch dust deflector plastic mounting brackets (there's a thin foam rubber sheet under the mounts that holds moisture, you're lucky if your truck doesn't have this port installed option)
Under port installed roof rack (look for orange stains coming out from underneath)
Around the rear hatch glass (under rubber gasket on the pinch weld)
Around the windshield gasket (more common if the windshield has ever been replaced)
Around/under the factory seam sealer where body panel skins are crimped (inner/underside edge of the hood skin especially the front/nose, door skins especially under the weatherstrip at the bottom of the door, rear hatch, lift gate)
Rocker panels, the rearmost section of the rocker panels is most common; hard to see with the running boards and plastic covers in place (look from underneath)
Very bottom of front fenders (close to the front doors) near two mounting bolts
Around/under the weatherstrip that seals the entire rear body opening (hatch/liftgate area).
Around doors and rear quarter panel glass (anywhere there's a weatherstrip on a pinch weld). Need to lift the weatherstripping up/off to check for rust
IME it's common across the top and the bottom of the rear body opening/door seal and often totally invisible unless the seal is pulled off.
Fuel Tank shield: IME if that has severe rust (like the vent holes are falling apart) it likely means there's a lot more rust elsewhere
Check the undercarriage, frame, bolt heads, and body mount brackets of course (don't be fooled by dirt/red clay)
