I’d factor in child care for your costs. Not knowing exactly where in Brooklyn you are, but I’d wager day care of minimum of $1k/month (very low end) to $4k+/ month per child. Nanny care is an option, usually starting around $4k a month.
I’d also caution about timing your purchase. NYC reality is cut throat in the best of times but recent mortgage rate swings have left a lot of people “locked in” to the places they refinanced during the early covid days. This makes new properties on the market a rarity and highly sought after. Keep your down payment as liquid as possible and try to keep the timeline on your own terms. You don’t want to be forced out of your building and looking for a new place at the same time.