I plan to breed BPs to get the morphs I want, and plan to sell snakes really only as a means of "breaking even" on costs and to cut down on superfluous animals. Ergo, the fact that your friend isn't making tonnes of money on the snakes isn't raising red flags to me...sometimes people who AREN'T in it for the money produce some wonderful animals. Plus there are some who care ONLY for the money, and not for the animals themselves, and I'd rather not buy from them even if they are making money hand over fist!
Breeders, big or small, should have the welfare of the animals in mind at all times, THAT is how I'd judge a "good breeder." Someone who care about the snakes, is informed and conscientious, and someone who cares just as much about making sure the snake is right for you as they care about the cash.
I met a breeder at a local reptile expo not long ago...not one of the "big names" out there. He breeds Balls and Beardies in his home, to supplement his family's income. He clearly loves the snakes and cares for them very conscientiously...the animals at the expo were all fit, healthy, beautiful animals.
A week later I drove to his home to pick out/pick up my little male Mojave. I got a FANTASTIC little '09 snake, got to see where he was hatched and how he was cared for, and to top it all off I got a REALLY great deal on the price. While gas-money to drive there cost almost as much as it would have to have the dang thing shipped to me, it was still worth it. I'm very confident in that breeder and would be comfortable buying from him again.
Buying a snake of ANY kind should be a good experience.