Hi Ben.
I got into instructing as a way to build hours before moving into the airlines which hopefully after three and a half years instructing shouldn't be too much longer. This is popular with lots of people looking to build hours before moving into the airline world, but you do find caarer instructors out there, it is difficult though to survive on instructor wages especially for PPL training, it does improve if you are teaching commercially, or for the military through DEFTS but this takes time and experience to achieve. Personally I get £18000 a year, thats as a PPL CFI, my instructors at present get a £500 pound a month retainer and £15 an hour for flying. There are better pay and conditions out ther but also much worse. Personally I love instructing its a great job and would recommend it to anyone, even if your goal is the airlines. You learn so much about flying, meet lots of great pople and gain an immense sense of achievement when your students go solo or pass their flight test. I for one will still be looking to instruct once I move into the airlines as its much more fun.
To go a little further I recommend going for a trail lesson, see what you make of it. If as I suspect its everything you thought it would be do your PPL. From there you will need to build 150 hours do the CPL or ATPL ground exams, do the CPL and then the instructor rating. So you are talking serious money to get to even the instructing point. At present though there does seem to be a dearth of instructors so after qualifying you shouldn't have a problem getting a job.
Hope this answers some of your questions, if you have anymore feel free to ask.
Regards,
Han.