Principle repayment is optional (when taking a loan). It only makes a small difference to interest rate [1]. So for the purposes of discussing cost minimization

Principle repayment is optional (when taking a loan). It only makes a small difference to interest rate [1]. So for the purposes of discussing cost minimization, it is legitimate to exclude it. [1] http://www.schwab.com/public/schwab/banking_lending/mortgages/todays_rates?cmsid=P-2266141&lvl1=banking_lending&lvl2=mortgages http://www.schwab.com/public/schwab/banking_lending/mortgage...