Ding ding ding. The difference between 2 incomes between 2 and 1 income for 1 is surprisingly large. Economy of scale kicks in for personal life very quickly.

Two incomes halves the rent/mortgage, utilities (not taking into account the extra usage), food is sold in orders of two for cost. Obviously if you throw kids into the equation this doesn't apply, but DINK living is a legit bracket changer.