>>39898921The closest thing we have as a source of starter Pokemon is the anime. There are two concepts at work, here. The first being that, starters are wild, albeit rare, Pokemon. That's how Ash will catch a few of them. Like, his Snivy and Treeko were both wild. But, take that with a grain of salt, because Ash has to have at least one starter for marketing reasons, and a Professor won't give him one when he's got Pikachu with him, so they'll always engineer a way to give him at least a single starter. Sometimes he has multiple, though.
The second, though, is the idea that there are secret breeding facilities hidden throughout regions. Starter species are still rare, but they're bred en masse for starting trainers, and the location of these breeding grounds are closely guarded because they're just that valuable. There's an episode about it in the show, somewhere during 3rd Gen. It's got a bunch of baby Mudkip in it, and I assume that's how Brock caught his.
In short I'd say coming from a family of Pokemon Breeders that raise starters for professors is viable, and interesting, but it should come with some drawbacks. This ranch ought to be isolated, hard to get to. Their home is way off the grid. The family is probably well paid, it'd be like a government subsidy farming sort of thing if they're being given out by Professors in a League-sanctioned breeding program, but they're also clandestine, closely guarded, and suspicious. I always think it's interesting for someone coming from a Breeder family to start out, not with a rare egg of some kind, but a more mundane caretaker Pokemon. A Numel or a Fletchling, something with Flame Body or Magma Armor, for example, that's the offspring of the breeding center's egg-warming Pokemon. After all, the eggs are for sale, and they're debatably not the breeder's property if they're hired by the League.