It is very possible to find a purebred at a shelter. Buy a purebred is not the only way to go. I've always had "mutts" and they are the best.
Yes, it is true that Persians require a lot of grooming. Their fur is much harder to take care of than other long haired breeds. It is because of the texture.
I didn't want to miss out on saying that I am very happy that you will be getting 2 pets. That is exciting.