Make sure the oil ports going to the tensioners aren’t plugged up either. Run a pipe cleaner in them to make sure they are clear. They will be a hole in the side of the hole the tensioners thread into.
Since the seller is saying the chains aren’t making any noise, they are probably fine but pipe cleaners are cheap and doesn’t take that much effort to use them.
I would also ask to start the engine with the hood open to make sure. Trust but verify. The seller may be honest, lying, or doesn’t know what to listen for.
Get any maintenance records you can and if the seller says “all they ever had to do was change the oil”, expect a lot of ignored or problems that may be hidden or haven’t shown up yet but might be evident with a visual inspection.
Like mentioned above. Be prepared to be doing a bunch of fluid changes if they can show they have kept on the maintenance. Transmission fluid, brake fluid, coolant, power steering fluid, axle fluid, and transfer case fluid if it is a 4X4 come to mind off the top of my head.