Stop thinking about it and just do it!!!!
I was a flying instructor for about 10 years. In that time my wages increased from £10 / hr (no retainer), to about £38,000 / year as a commercial FI.
I have worked all over the UK and spent a few years instructing in America. What a life!
You really need to target the big schools if you want to make a career out of it. You can also add examiners ratings etc.. if you really want to go to town.