Way back in the dim and distant past when one could still get jump seat rides (about 2 years ago I think), I was asked by the Captain if I was planning on going commercial. Then in my forties (now you wouldn't ask a lady her exact age would you
) I replied that I was too old. He told me about someone who got his first airline job at age 54, and was now approaching 60 and still flying for a living. So it can be done. But as others have said, whether you'll ever recoup your investment in financial terms is a different question.
Still, it made me reconsider, and decide to follow that dream...