I see why you're hesitant, if I bought a pair from a breeder I wouldn't feel like I had contributed anything in the way of improved genetics or anything. I guess if it were me, I'd need to breed their spawn before they felt like mine, as I would be the one selecting for traits at that point. But if I buy two fish from different breeders and breed them, then their offspring already feel like "mine" because I selected for traits in their parents. Does that make sense?
I suppose I wouldn't consider myself to have an actual "line" until I was getting colors and form to breed true.