I run a mentoring organisation which I started because of my interest in teaching. I used to help the graduates find jobs that they liked. After a couple of years, I started a small services company of my own and started to hire mostly out of my own student pool. I'm very happy with the decision. I develop rapport with the students (and later employees). A 4 month training program, while beneficial for the students,…
Junior people around the world get to benefit from the mentorship, and we get access to talented people early on. Without that much internal risk, since it's open source.
The problem is exactly as you describe: scaling. Mentoring is an extremely time-intensive process and when things go rough, such "charity" activities are the first to suffer.