First, maintenance history is key. Oil, trans, diff and coolant changes on a regular basis. Shock rebuilds or replacements on a schedule. Plugs, coils and wires should be done every 70K or so as well. Rust is also a big issue for a lot of these trucks depending on where you're located, so be sure there are no issues there as it can be very costly to repair a rusted cab corner.
I wouldn't worry too much about the truck being driven hard. I bought a 2013 with 170K on it in December that had been used off-road quite a bit. That said, it was upgraded to handle it well and was extremely well maintained. I've since put almost 20K miles on it and trust that it will be a solid vehicle for many more miles. I would consider what you plan on using the truck for and try to find one that has been upgraded appropriately. I bought mine with King 3.0s all around, upgraded UCAs and deavers. These upgrades would have cost me almost 10K to get done and I knew I wanted them as I planned on using the truck for harder/faster off-roading. I didn't pay anywhere near $10K more than market value for the truck, so the upgrades were essentially free. For reference I paid $24K for the truck.