Usually loan officers start out with a small base pay for a few months. When that time is up the base pay usually goes down and they are paid mostly commission. It really depends on what type of loan officer you are talking about, how much experience you have, if you are a good sales person, what state you are in and if you are in a metropolitan area or not.
Go to monster.com and use their salary calculator to see what they pay in your area. In the midwest the starting salary is about $35K and personal and $45K for commercial. Usually if you are just out of college you will be assigned a position like credit analyst for a few years until you have learned the business.