He says he leaves his box (maybe brood box) at my place for a couple of days to let the bees 'set' themselves to their new home.
Maybe I do not understand but as I read it you say he will move his brood box to your place along with your new bees to prevent the drifting. Your new bees will orient to the location in his yard were the old box (parent hive) was located. And the bees from his hive he plans to move to your yard as a helper will also orient back to his old yard. That is if I understand your move.
The question is how $ is this actually an investment for you personally. And you have already stated the fellow is less than desirable to do business with. Having or not having the bees or risking catching a swarm are the key. Weigh your options???
I went to his place today. He has many nuc boxes. He said he will leave one of those at my place for a couple of days, and once that nuc gets oriented to my location, he'll move them to my new hive.
Interestingly, he has guaranteed that the strength of the colony will not be dropped. If I see any decline in the strength within a week, he'll exchange it with a new colony. Deal sounds acceptable; doesn't it?
And regarding money, it's Rs. 650 for the colony (an equivalent of around $10.5). It's a solid figure for me.