Check the fabric for any mould or water damage/staining. Try out all the zippers and make sure they work, and don't pop off their tracks. Check the base fabric around the bottom where the zipper goes around to zip up the cover for fraying/signs of the zipper getting caught. The ruggedized have a good floor base, so there shouldn't be any dents to watch out for. Make sure the outer cover is in good condition as in no holes, wear points and the UV cover isn't faded (good sign of age). Check the ladder out, make sure the locking pins are in place and no bolts are missing. If the tent has an LED light, check the battery, or power connector point. Also a big one is to check all the bug screens for holes!
Beyond that, good luck and hopefully you'll find a deal! I don't know what the used prices are on the ruggedized models are like where you live but I occasionally see one around $2K to $2.5K used around here in Alberta Canada. I never bought one before as only the orange ones go up for sale, and I don't like waking up in an orange tent when the sun is out. I prefer more traditional colours.