You may have a valve cover or something that is leaking a little. If that oil drops on exhaust pipe, you will definitely smell it.

Is it expensive to fix an my oil light comes on almost all the time

Is the oil level full? Double Check your oil pressure. If you can find the leak, if you fix it yourself, no labor costs. If you take it to a shop you will pay labor and parts. Different shops charge different labor rates. You can call different shops try to get an estimate. It may be hard for them to give you an estimate without looking at it ?