The human race will survive a LOOOOONG time with one child per couple. This being said, I’m assuming you can comfortably afford your 0.8 baths per human. And were able to afford them when you bought them.
If you’re single, this begs the question of (if you’re buying a family-sized house), why not buy a duplex? You can live in one apt, keep the other one rented while you’re single, then take over the second apartment as your family grows.