If you knew some good LFS in your area then talk to them, folks often giving them free tanks but beware some jerk LFS would turn it around for massive free profit. For craiglist you have patience and time and so called "Luck" to get what you want for cheap, for some places Craiglist is a business warfare because of stupid easy money flip for profit.
If you are planning to buy a new tank then consider to buy 150~180 (60x24x24 or 72x24x24) gallons tank, you will open up more option of species to keep than a 125G, trust me if you into fish keeping then don't settle with a standard 125G and then regret about few days later...yes, few days later not even weeks or months.