Read the book The Simple Path to Wealth, or the basics in this blog post.
http://www.mrmoneymustache.com/2012/01/13/the-shockingly-sim...
>...The 4% refers to the portion of the portfolio withdrawn during the first year; it is assumed that the portion withdrawn in subsequent years will increase with the consumer price index (CPI) to keep pace with the cost of living. The withdrawals may exceed the income earned by the portfolio, and the total value of the portfolio may well shrink during periods when the stock market performs poorly. It is assumed that the portfolio needs to last thirty years.
The important part is that there is absolutely no guarantee that "you can withdraw 4% forever." They found that in the different time periods they studied that taking 4% would mean the portfolio would last 30 years before being exhausted. That might be fine if the person works to 65, but might not work out very well if they retire much earlier. (The paper also allowed for increasing the amount taken due to inflation, so if you can survive on the 4% the portfolio should last longer.)
I've been looking into several private REITs in the past, and their return is indeed in the 10% ballpark (usually 10% is the ceiling), mostly distributed as interest income. The problem with that is that if you don't hold them in a tax sheltered account, your 10% will easily become 5% after taxes, since interest income is taxed at your marginal rate, so if you're at the peak of your earning career in a coastal city, 50%+ marginal tax rate is not at all uncommon.
In comparison, broad cap index funds are much much more tax efficient via qualified dividends and long term capital gains, so to get 5% after tax from those you need much less than 10% returns.
I decided to give up on investing in private REITs, I don't like the idea of taking a substantial amount of risk just to then send all the premium to Uncle Sam, and being a traditional W2 employee, access to self directed IRA is not worth the trouble.
Many people (not saying it's you) like to boast about their pre-tax return: the only thing that counts is how much you're keeping after taxes.