Excel Millionaire

So in my Accounting class the other day we were discussing investments. We discussed the avenue of becoming a millionaire by the age of 70. I have heard of that process several times before from my older siblings and it excited me of course then but I think now that I am older I felt a bit of urgency. The excel spreadsheet that our instructor brought up was I believe 1200 dollars a year at 8 percent. And at the age of seventy, voila`, you are worth over a million dollars. So after analyzing that for awhile, I figured that I want to be worth that in less than 40 years and more like 15 years! And of course that means that I had basically two options that I needed to optimize. So the easy one was I thought, well lets try and just double the amount of money invested per year. So I plan on investing 2500 dollars a year, but then my other dilemma had to be solved and that is of the percent of money that will be working for me. And I know alot of folks wont believe this but I have figured a way to make 16 percent on my investments. Well its not exactly perfected yet, however I have seen it produce 16 percent for 5 consecutive years and I hope to cash in as well. I dont really want to give away this secret until I have it producing at a contstant flow for me but it has to do with real estate.