$("#bbie_income,#bbie_payout").bind("input change",function(){

var bbie_income = $('#bbie_income').val()?$('#bbie_income').val():0;
var bbie_payout = $('#bbie_payout').val()?$('#bbie_payout').val():0;
var bbie_ending_balance = bbie_income - bbie_payout;
$('#bbie_ending_balance').val(bbie_ending_balance.toFixed(2));

});