20% annually sounds like a very high return to me. I think that this could only be achieved by active investing.

Anyways I think that your problem is not accumulating $1mln, but generating a decent amount of cashflow. Let’s say that you can live well on $40,000/year. At 4% and 1 million dollars you have reached financial independence.

So how can you reach $40,000 in income in 15 years? My answer is to invest in dividend growth stocks. You could easily create a dividend growth portfolio yielding 4% in the current market, where dividend growth rates could be around 10-12%. At 12% your dividend income will double every 6 years. In 15 years your dividend yield on cost will be about 20%, and that’s assuming that you don’t reinvest your dividend income. If you do reinvest, your income will be a lot higher

So in order for you to reach $40,000 in income in 15 years, you need to invest 200K now.