After 20 years of instructing part time I tried full time over the Summer to see if I could get close to a level of earnings that I could live frugally on.
Mostly it was about giving myself the Summer I had promised myself for a long time but it was also an experiment to see if it might work longer term.
I thought I might get somewhere close over the summer but, actually, not a hope.
It'll have to wait until I've got much, much more money in the bank.
The problem wasn't so much to do with the peak earning level - mine is one of the better hourly paying PPL schools - it was more about the level of time commitment I need to make in order to get some chargeable hours. I had imagined that I might be able to do something else to earn a few pennies when either there is bad weather or when I'm short of students. In practice, while I was able to arrange my own timetable and only turn up at the airfield if there was something to do, I could not plan ahead sufficiently to make myself available for other activities. In order to get flying hours I must commit to being available for flying and then, when I find I'm available for something else, it's too late.
I also find myself putting quite a few more hours than I expected in the evenings etc. managing student queries and timetable changes.
So the effective pay rate after including commited but not spent days and extra homework is absolutely dire even though the hourly flying rate is pretty good.
So, Nurse2Pilot, my experience is consistent with your suspicions - and that's with all of my own training costs written off a long time ago.
Having said all that I have had the most wonderful Summer and don't regret it for a moment and can now go back to part time instruction and have the most incredibly rewarding job without having to worry about it paying so little.
I suggest that if you think you might enjoy instructing then you do the same.