Hi Donna and welcome to the board, I'm glad you decided to bring your search over here.
A couple things I wanted to add:
"I have contacted numerous breeders, but either they don't have kittens at all, or they are on the way and I have to wait two months."
Any breeder who lets you take a kitten at 8wks is not a good breeder. Keep looking! Also, in the overall scheme of things having to wait a couple months for the right kitten from the right breeder isn't much. I waited 6 months for my Ruin to come home and she was more than worth it!
"How do I know a good breeder if I purchase online?"
"How can I tell if the breeder is reputable and doesn't line breed."
In this instance you would need to do tons of research and ask tons of questions. Ask for references and follow up on them. Call people who have adopted kittens from this breeder in the past, call their vet, check out their website -- some people are very good at deception, so be careful if you go this route. Also, the questions the breeder asks you can speak volumes.
As for line breeding, I'm not a breeder but it is not necessarily a bad thing. If there is a particular trait a breeder is looking for, line breeding gives a better chance at getting it. BUT if there is a negative trait it also doubles the chances of getting that as well. So if you find a breeder you like otherwise, just ask their reason for line breeding.
"What about returns?"
Ethical breeders will ALWAYS take their kittens back, no questions asked, but you will not be entitled to any money back. They should also be willing to work with you if a kitten falls ill just after you've brought it home, or due to something that is covered in the contract. Most breeders will not return your money if after a period of time you decide the kitten is not for you, even if this is just a couple days after you've brought it home.
HTH and good luck on your search!