My husband and I had two kids because we (1) both have union jobs with decent worklife balance, and (2) had high quality yet reasonably priced daycare in our neighborhood. (It still cost us more than our mortgage when both were in daycare.) If we didn't have that we'd have only one kid and still make some pretty big sacrifices (we both really wanted kids). I truly don't know how other people do it without kind, generous family members nearby or very high paying jobs. ETA: We know A LOT of families with only one kid.