Firstly, 43 definitely isn't mid-life. I define middle-age as someone a few years older than me and it's working well. On a more serious note, at this age most people have family commitments and responsibilities so it's important to have sufficient financial security to take you through the early phases as restricted and basic instructor where, as previously mentioned, the remuneration is risible and your outlay to get the rating is significant.
If you can handle this, and the fact that, even at senior instructor level, the pay is relatively modest, then go for it. It is a wonderfully rewarding job. I've done my time in the RAF and the airlines and instructing is still what I enjoy most.
