Depending on the mechanical knowledge off owner, I can answer just about any question they ask. One lady asked about her feed dogs not going back up, some machines will not go back up unless you turn the wheel over, (start sewing). It sounds simple but sometimes you never think of it.
I've been servicing sewing machines since 1989, I still service machines for Northwestern Ontario Canada. It is a large area with little or no service people and I can usually tell on the phone if it can be fixed by the owner.
I took a 2 year apprentice course with a dealer who was looking to teach and hire. I worked for him for 8 years before moving up to the Northwest, Red Lake area of Ontario.