I am not sure about breeders in your general area. Usually reptile shops will have reptile expos advertised which is a really good place to meet local breeders.

As for things to look for. It is pretty easy to spot if something is wrong with the snake. Skinny and malnourished. Popping, wheezing, limpness are signs of an RI. Size can also play a big part. The breeder should know or at least have a general idea of when the snake was hatched. You have a good idea that the snake may have feeding issues if a snake is 500g but 2 years old. It is always good to inquire the breeder of this to see if the feeding issue is resolved. Stuck sheds may also be something to look for. I usually will still purchase a snake with a stuck shed, but I also know how to fix the issue. Someone new to the hobby may want to stay away from a snake who has a stuck shed, especially the eye caps. Also the gender. It is good that you ask the breeder to either pop or probe the snake before taking it home just to be sure you are paying for what you purchased. Most knowledgeable breeders should be able to do this. Females are typically more expensive then males. Of course this is not always the case if you are getting a snake shipped. In this case you may want to inquire about pictures.

Most well known and high end breeders have healthy snakes and buying from them should have no problems. It is a good reason why you should avoid petshops chains like petco, Pet Smart and so on. Another good place to find breeders in your area is world of ball pythons. They have a list. Not all breeders are on it but many good ones are.