I would second what the others have said. At the end of the day, looking at it another way, if you try false economies you may end up losing the money you pay for it altogether.
Can you not go and have a look at it prior to buying it ?
bah i dont think theres anyone in carolina here does this look like a good buy at current price and up to what number (im not made of money if it goes above 100 ill have to borrow from parents) http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... %3AIT&rd=1
Firstly Bud, if the tank arrives or you go and pick it up and it isn't advertised as described (ie the advert doesn't mention a crack but there is) then you are within your ebay rights to refuse to purchase it.
Repairing tanks isn't particularly hard, althoguh it does depend on the tank to a degree, but the ones shown on your ebay advert are simple as to repair. The support brackets top and bottom are plastic and should just lift straight off, with a bit of encouragement anyway. Once they're off it just leaves a simple 4 sided glass tank....as long as you have some room, a few razor blades, silicon and some G-clamps it's a fairly straight forward process. You should just be able to search for the process of how to repair a tank on the web.