If you find one look it over good and make sure it doesn't have any obvious holes. I have a friend that bought a used tank, filled it up and found out the hard way it had a leak after it was full of semen.
I bought mine used for $150 from my local genex guy.
He was transporting a tank last time he stopped for sosmeone else. If you know the Genex/ABS/etc... people in your neighborhood ask them. They will know whos tank is good. Mine was from a retiring Dairy Farmer..
thanks for all the input...I'm not sure what all to exactly look for I'm just trying to help out my brother since he lives away from the farm. i really appreciate the input!
thanks Bridget