--- THERE IS/WAS A FRAME RECALL FOR SOME OF THE MODEL YEARS YOU LISTED ---
USE THESE:
http://www.toyota.com/recallhttps://www.toyota.ca/toyota/en/secure/company-info/vehicle-safety/recall-alertsIf there's still an outstanding frame recall for the truck you're looking at, be very weary. Look along the frame's whole length, take note of the present corrosion.
If it looks excessive or holes are present, stay far away, it will only get worse. Toyota only gave a certain time period in which they'll replace the frame or buy the truck back.
If there is no recall or the recall's been done already. Examine the frame anyway, it doesn't hurt to do it.
Now that that's out of the way, there's no real things that it needs that stand out. Regular maintenance stuff, like any other vehicle.