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When can you use existing real estate as collateral to buy more?
@victor has the most descriptive and basic idea on how this is done.  The only thing I would add is that one benefit to real estate is that you can control how much the property is worth.  By increasing rents and making the property one of the best in the neighborhood, you increase the value. As for the comment that this is the type of investing that caused the 1929 stock market crash, there are many other aspects that are overlooked.  Taking equity out of real estate has been happening long before and after the depression.  People do it all the time by taking out home equity loans, just not everyone uses it to purchase another investment.