Even if you looked for kegs from a reputable online source, they are going to be used, they will cost you the $100 without shipping. You will want to replace all of the rubber gaskets, which you can do all 5 for about $10 bucks. Just check to make sure they hold pressure first. Having to replace pressure release valves and lids that don't seal can get pricey.
$100 for the entire lot is a steal