Der_Echte is a unique character who has an interesting approach to coaching and I think he may be an exception.....I would also say NextLevel is as well. These two work with people very differently than what you might think of as a standard coaching model and they are very effective at working with ADULT Learners.
So, I just want to give you a bit of a warning on this advice.
I am a weird character who has turned more than one hobby into a career. It is worth being cautious with this. It could be great. But it also could cause you to lose interest in the hobby. I used to skate ramps and was sponsored and sent to competitions and then I skated ramps in Ringling Brothers and Barnum and Bailey Circus as a performer for a few years. When I stopped doing that, I still loved skating. Why I stopped was that the risk was too big once I had kids. That was my calculus on that subject.
I am currently and have been since I left the circus, a yoga teacher. I would say, a lot of what I do is actually movement analysis and neuromuscular repatterning to help people use their bodies more functionally. I have to say, what I do for a living, I have never done anything I enjoy anywhere near as much.
But with table tennis, I would warn that you have to be a particular sort to love coaching TT the someone like Der or NL do. But it is worth knowing that, TT is one of the most aggravatingly technical and complex sports ever invented. When you look at someone who is trying to learn, and do something simple like a FH Loop, you will see thousands of things that all need to be fixed. Limiting yourself to just a few things that person needs to work on can be challenging and if you throw too much at a student, they simply won't learn any of it. Also, in one session a student can learn something and look great; and then the next time you see them, they have unlearned that and are back to the old habit.
With how complex and frustrating TT is for a coach trying to help a student, you also WILL NOT BE playing TT yourself while you are coaching. So, some who start coaching start feeling they are wasting their own time and their game is stagnating as a result.
However, if you are like Der_Echte and NextLevel and really like and enjoy the problem solving aspect of figuring out how to effectively get a TT Enthusiast to go from one level to another, that would be the reason to look into coaching.....but you would not be doing much playing of TT while you are coaching.
I just want to make sure you are clear on that.