It depends on how the mortgage is structured.
A saying to help you remember the portions of a mortgage: Have PITI on me, oh mighty banking institution!
P - The
PRINCIPAL of the mortgage (what the home costs)
I - The
INTEREST you'll pay to the lending institution (for trusting the borrower...you)
T - The
TAXES owed to the local government (varies by local services availed to you such as police, fire, schools, etc, and usually held in escrow by the lender)
I - The
INSURANCE (always less if you can put down more than 20% of the principal)
Those are the 4 components of a mortgage. Now, as to whether it's best to pay off early or not? Only if there is no balloon on the end.
- Speak plainly and bluntly with your real estate agent.
- Emphasize, with white boards and colored markers if necessary, that you plan to pay off early.
- Tell them, don't ask if it's alright, but TELL them you will not enter a loan with any early payment penalties.
All realtors and loan institutions want your
money.
Your job is to find the ones who want your
business.
The difference between the two schools of thought is key.
You're the boss hiring them for their services. You do not work for them: They work for you.
Again, use the white board and markers if they do not understand this empirical fact.

Hope that helps