Expendable
==========

This is a program for modelling home finances. In particular, it can
be used to work how long it will take to pay back a mortgage if a
linked "offset" facility is available.  Offset accounts are like
savings accounts, but instead of accruing interest they reduce the
amount of interest charged for the mortgage by offsetting the loan
amount.

For example, if you have a loan amount of 100,000, but your offset
account has 10,000 in, you will only be charged interest on the
outstanding 90,000.  If your mortgage interest rate is 5%, that means
that you'll effectively be earning 5% interest on 10,000.  As it
reduces the amount of interest charged rather than earning savings
interest, this is not taxable.

You can achieve a similar effect yourself even without an offset
mortgage, so long as you can find an account that pays more interest
(after tax) than your mortgage charges.

The data model for this is a tree of accounts.  For example:

  Mortgage
  +-Savings account
    +-FTD

Having a parent in the tree means that the account will be used to pay
into the parent.  Above, a fixed term deposit account will pay into
the savings account on maturity; the savings account will pay into the
mortgage when sufficient funds have built up to pay it off.

Tim.
*/
