Too old?!
Trust me, when you get to 70 you'll be wondering why you even asked the question.
I'm on my 3rd career since I was 40 well over 30 years ago, and they have all been great fun, completely different, and fairly profitable, in spite of all being loosely aviation-related apart from one when I tried to break out of aviation and managed a fleet of 12 charter yachts for 5 years. (Hugely enjoyable, but not profitable so I sighed and went back to aviation.)
If you want to do it, you sprog, go for it. You have at least 30 years useful life left. I'll tell you in 10 years time if that should be "at least 40 years left".
Ah yes, the "poor health" problem. How poor? Does it prevent you studying and working? If not, it's not an issue. If it does, then ignore the advice above.