Does he breed the GTPs himself too? If not, can he garauntee where it came from - as in who bred it?? If not, it is almost certainly a farmed animal or from wild-caught parents. The most important piece of advice I can give you is to only buy a GTP from a reputable breeder! It is even more important to do this with GTPs because there are so many farmed animals out there and there is little documentation on them.
I understand about the money. $400 is a lot for me too. But that's why its even more important to buy from a reputable breeder - even if you have to pay a little more up front. You'll spend less in the long run. I mentioned both Ryan and Allie earlier because they are very reasonable and have excellent captive bred and born stock with documented lineage.
GTPs are not ball pythons. Just because you can raise a tiny baby ball doesn't mean you'll do well with a baby GTP. I have raised numerous boas starting with babies as young as 6 weeks old and only at 110gm and I am hesitant to raise a neo GTP. You are best off starting with a yearling. You'll still see a lot of color changes.
Exactly.