MortgageBuddy

This gem will calculate APR and Amoratization.

Installation

Add this line to your application's Gemfile:

gem 'mortgage-buddy'

And then execute:

$ bundle

Or install it yourself as:

$ gem install mortgage-buddy

Usage

loan_amount   = 550000
interest_rate = 3.0
period        = 360 # 12 months * 30 years
fees          = 600 # $600 closing costs
points        = 0 # no points to get this loan

mortgage_cost = MortgageBuddy::MortgageCost.new(loan_amount:   loan_amount,
                                                interest_rate: interest_rate,
                                                period:        period,
                                                fees:          fees,
                                                points:        points)
puts mortgage_cost.apr # 3.01% (rounded)
puts mortgage_cost.monthly_payment_with_fees # $2321.35 (rounded)

amoratizer_30_year = MortgageBuddy::Amoratizer.new(interest_rate: interest_rate,
                                                   loan_amount:   loan_amount,
                                                   period:        period)

puts amoratizer_30_year.total_num_payments # 360 or 30 years (no extra payment)
puts amoratizer_30_year.total_interest # $284,773.56 (disturbing)
puts amoratizer_30_year.payments # an array of openstructs with every payment amount, interest, principal, etc

# Now let's see what happens when we pay extra
amoratizer_with_pay_extra = MortgageBuddy::Amoratizer.new(interest_rate:         interest_rate,
                                                          loan_amount:           loan_amount,
                                                          period:                period,
                                                          extra_monthly_payment: 1000)

puts amoratizer_with_pay_extra.total_num_payments # 215 or just under 18 years
puts amoratizer_with_pay_extra.total_interest # $161053.35
puts amoratizer_30_year.total_interest - amoratizer_with_pay_extra.total_interest # a savings of $123720.21

# What if we can get a little bit lower rate on a 15 year?
amoratizer_15_year = MortgageBuddy::Amoratizer.new(interest_rate:         2.9,
                                                   loan_amount:           loan_amount,
                                                   period:                180,
                                                   extra_monthly_payment: 0)
puts amoratizer_15_year.total_num_payments # 180 15 years
puts amoratizer_15_year.total_interest # $128,923.59
puts amoratizer_15_year.actual_monthly_payment # $3771.80
puts amoratizer_30_year.total_interest - amoratizer_15_year.total_interest # a savings of $155,849.97

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/mortgage-buddy. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.