Mortgage Calculations

# monthly payment
def monthly(loanAmount, interestRateQuote=0.04, years=30.0):
    months = years*12.0
    interestRate = interestRateQuote / 12.0
    # Formula to calculate monthly payments
    mortgagePayment = loanAmount * (interestRate * (1 + interestRate)
                                    ** months) / ((1 + interestRate) ** months - 1)
    return mortgagePayment

# break even for closing cost
cost_help = 10000 # closing cost help
downpayment = 0.2
other_fee = 0.02 # factoring in tax, fee increase
offer_factor = 1.0 # can increase this to play with offering more than the help on closing costs
mortgage_rate = 0.0425
months_in_year = 12

# break_even in years
cost_help * (1 - downpayment - other_fee) /(monthly(cost_help * (1 - downpayment) , mortgage_rate ) * months_in_year)

# break even point of buying down/up rate
principle = 448000
# buying down
mortgage_rate = 0.0425
points = 0.0075
rate_incr = -1/8.0/100.0

# buying up
mortgage_rate = 0.045
points = 0.0025
rate_incr = 1/8.0/100.0
principle * points /(monthly(principle, mortgage_rate ) - monthly(principle, mortgage_rate + rate_incr ))/months_in_year