The wisdom of paying off loan?

[Bryan Lester]

My specific question is the basic idea of how a loan works. Any further elaboration is appreciated.

Say I get a 100K loan on a 120K house. The monthly fee I am paying for this loan includes interest, property tax, insurance (if applicable), ect. My question is on the interest portion. Lets say the interest rate is 5% for a 30 year fixed rate.

As a simple example, if I just pay the entire 100K loan off the first year, would I only owe 5K in interest? OR would I owe interest for the entire 30 year period, amounting to something like 150K?

This is a concept I haven't been able to get a clear answer on from lenders so I turn to you for help.