Have you read The Unincorporated Man? It's a sci-fi novel about a society like the one you're suggesting, where "investors" in humans such as parents and educators own shares in the person's future earnings. The novel/series casts this in various lights, mostly negative but with undeniable fairness and benefits. One question is where these shareholder cross the line into slaveowners. What is a reasonable rate of taxation? What can be reasonably demanded from the indebted?