Well, yeah, that's something I do for all my towns. I don't need any random immigrants, at least not as residents. My game will still produce sims it thinks it needs in careers with no other members, but those stay homeless. I don't remember exactly where this was done from the top of my head (or rather, it's easy to confuse the settings for role sims with those for residents), as I've had it in my SP settings for ages now, and I always just copy those over.
A good start is always here:
Population - Town ManagementUsing Porter to place your extended family in a blank town (well, nearly blank, as you need at least one sim there as anchor to invoke the "Unpack" command) is oddly satisfying.
