I am a hobbyist. I do not feel “expert” enough to sell my upholstery skills. But I got great satisfaction from doing my own.
The nice thing about doing your own upholstery is that, for the cost of materials and your time, you can learn to do it, and do it over again if you don’t like how it turned out. I had no sewing experience, bought a Sailrite machine with servo motor, practiced a few seams guided by YouTube videos, then built a seat cushion set for our beat up golf cart as practice for doing my Model A interior. The golf cart set is imperfect, but has been presentable enough to get compliments from those who have seen it. My Model A interior has received many compliments, but I won’t post it here so as not to offend the purists, as it is not a restoration, but a simple two color vinyl hot rod style.
Take it one step at a time, and you can do it.
One warning that I learned from my time on upholstery forums is that you may not want to use the old covers for patterns, as they may have stretched over the years. Sailrite sells a clear plastic material that is ideal for making your own patterns. Use the old covers as a guide to the separate panels you’ll need, but make your own patterns from the structure you’ll be covering.