Fins are all torn up and look like they went through A LOT of stress... That alone is a clear indicator of a fish not to buy... Always look for healthy fish when making an important purchase, specially with arapaima them being so skittish when young regarding feeding and stuff... If I was your friend I wouldn't risk buying that fish. One thing I learned with arapaima is that there's a time in life for you to have one, I personally spent almost 6 years trying to find the perfect arapaima, missing a lot of oportunities due to monetary reasons or just because of me not being able to keep one at the time. Your friend does have a good growout tank now, but all he has to do now is wait for the perfect arapaima to come!