What it means to "buy down a mortgage".

Buying down a mortgage means paying off part of the loan principal early. You can do this by making extra payments or taking out a home equity loan.

Borrowers who have substantial savings and feel comfortable with their ability to make extra payments may wish to consider buying down their mortgages. Doing so can reduce their monthly payments and shorten the length of their loans, which can be helpful if they plan on moving in the near future.

However, there are several drawbacks to buying down a mortgage:

The funds used to buy down the mortgage must come from outside sources or be taken out in a home equity loan. If you do not have money saved up in an emergency fund or sufficient reserves in other investment accounts, you may need to use funds that were earmarked for other purposes (such as retirement savings). Also, if you take out a home equity loan for this purpose, you will need to make monthly payments on that loan until it is paid off.

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