As for "careers in science", what can someone later in life (I just turned 60, can't believe it) still do? I have a CS degree from ages ago, and have a scientific mindset (runs in my family, e.g., my sister was a research scientist [mathematician] before retirement). I don't want to retire anytime soon. But I'm unlikely to get into grad school. I can take MOOCs of course, and do. My interest in science tends toward neurology and embodiment.
Of course there's a chicken-and-egg problem here, where the stronger your research record, the more busy researchers will want to talk to you, and the more they'll talk to you, the stronger you'll be able to make your record. Just like with dating or anything else, I guess, it does take persistence to break this cycle. :-)
And of course, you'll need to be considerate of people's time, and you'll need to decline to take it personally if some people are too busy to answer you. Just plow ahead and ask others.
Lastly, let me strongly suggest finding some other people who started their research careers later in life, and asking their advice. They'll surely be able to think of things I didn't!