If at all possible request to see the tank. If your getting a complete setup ask how long its been setup. Ask the history of teh tank. Find out the husbandry skills of the current owner and how they treated illnesses if the fish had any, etc. If the tank is a fish only system find out if they ever used copper in the tank for medication.
By seeing the tank you will have a good idea for the tanks quality. Find out how old the lights are. If the bulbs are older than 6months plan on getting new bulbs for the lights anyway.
If your looking at getting a tank thats been taken down and put into storage ask if they can fill it with water prior to your arrival so you can verify it does not leak. Look for cracks or serious damage to the corner and bottom seals. Look for scratches on the glass or acylic.
For moving the tank look at our articles area. There is a good article on moving a FW
tank. The basics will hold for SW
aswell. Never try to carry more than 5 gal
of water at once. Drain the display tank as much as possible before attempting to move it. Use rubbermaid trashcans on a box truck or pickup truck to transport the water. FIll them about 1/2- 2/3ed full and make sure they are securtly strapped to the sides of the truck. Going around a turn and having a couple hundred pounds of water shifting can cause control issues.