43 is not too young to get started at all. But, an airline career may or mat not be what you would want to do. Lots of different ways to fly professionally, corporate, charter, flight instructor, etc. Flight instructing perhaps fits with a part-time scenario better than other gigs. Sounds like you're on your way to getting started, and it sounds like you have a reasonable approach. My advice, especially for "older" folks, don't quit your day job, don't go into debt for flight training, take it one step at a time, and have fun!