He never explicitly gives any advice for acquiring net income generating assets, but reading between the lines (and given the context) the advice is to pursue entrepreneurship. While I strongly encourage people to pursue entrepreneurship when it makes sense for them to do so, I don't think it's a substitute for proper retirement planning and long-term investment as this article seems to suggest. And it's certainly not good retirement planning advice for anyone who doesn't already understand the basic differences between money, wealth, and assets as this article seems to imply.
Given the failure rate of entrepreneurs and start-ups on average, it seems quite strange to dismiss traditional retirement planning and long-term savings as too risky while encouraging entrepreneurship as the solution in the same article. Traditional retirement investment vehicles (low-overhead diversified ETFs with a mix of bonds, ratio depending on years until retirement, combined with taking advantage of tax-advantaged accounts such as 401Ks, IRAs, etc) isn't anywhere near as risky, especially over the long term. Remember, a single stock market crash in your 20s or 30s is going to have virtually no impact on your retirement savings in your 50s and 60s. When saving for retirement, you have to consider the timeframe involved. By the same token, risky entrepreneurship isn't all that risky when you're young.