A bi-weekly payment plan accelerates loan payoff because 26 half-payments equal 13 monthly payments — one more than the 12 you'd make on a standard schedule. That extra payment goes entirely to principal.

On a typical 30-year mortgage, switching to bi-weekly payments shaves about 4-5 years off the loan and saves tens of thousands in interest.

You can usually achieve the same result without a formal program by simply adding 1/12 of your monthly payment to each month — both approaches put one extra full payment per year toward principal.