I can't offer up any advice about whether or not this kitten is purebred. I don't know enough about breeding/genetics to throw out theories about the father.... but I will say this:
Whether or not OP buys this kitten - no matter what, it needs a home. If OP doesn't buy it, some one else will. OP (amstar2123) has said no matter what, she loves the kitty and wants to provide it a good home. In my very humble opinion $600 is well worth the vaccines, vet examination, and the one year guarantee on kitty's health.
How far away is the breeder from you amstar2123? Any chance you can have a visit to see mama, kittens, and hopefully daddy before you make the purchase final? That might help alleviate some of your concerns.
Whether or not OP buys this kitten - no matter what, it needs a home. If OP doesn't buy it, some one else will. OP (amstar2123) has said no matter what, she loves the kitty and wants to provide it a good home. In my very humble opinion $600 is well worth the vaccines, vet examination, and the one year guarantee on kitty's health.
How far away is the breeder from you amstar2123? Any chance you can have a visit to see mama, kittens, and hopefully daddy before you make the purchase final? That might help alleviate some of your concerns.