A prime swarm is no doubt the cheapest option, but as a new beekeeper you might lack confidence in collecting a swarm. Some commercial beekeepers offer TBH nucs although these can be expensive.
I tend to disagree, 'conventional' methods of beekeeping can be off putting not least the sheer...
If the colony is that infested and weakened it could be argued he kill and burn them thus removing all signs of disease from that hive. He would have to scorch the hive parts afterwards.
Start over again and learn from his mistake!!!!!!
I have been using nationals for years, after a little experiment with commercials, and have found double brood boxes to be preferable to brood and a half. The main advantages I have found include uniformity of frame size which is ideal when splitting colonies and manipulating for swarm control...