Well I will try to keep this short since it is a touchy subject for me.
Hellbenders are relatively easy to keep alive, but fairly difficult to keep thriving. I definitely would not encourage anyone to keep them unless they have 1000.00+US to invest on equipment with the goal to breed them (the only good reason to have them). Also PLEASE do not support the commercial collectors!
Jesse, your case is different since this is a "second hand" hellbender. You will need a tank of at least 75 gallons and a 125-200 gallon tank is more ideal. A couple canister filters and some airstones will work for filtration. Powerheads are good to move the water, but they also add heat to the water. A good chiller runs 600.00+US, but you might be able to get by with a 300.00 thermoelectric unit(they can only bring the temps down by 5-10 deg though). If the water is moving well, they can take temps around 75 in summer, but lower temps are obviously better.
We can get into feeding, etc... if you decide to take the animal.
hope this helps some.....