If you want to buy a stock, you have to pay the full value of the stock at the time you place the buy order. 

Even if you are buying on margin, the amount you can borrow is still much less than with real estate.

Most "conventional" mortgages require 25% down, however, depending on where you live, there are many types of mortgages that require as little as 5%. 

This means that you can control the whole property and the equity it holds by only paying a fraction of the total value. 

Of course, your mortgage will eventually pay the total value of the house at the time you purchased it, but you control it the minute the papers are signed.

This is what emboldens real estate flippers and landlords alike. 

They can take out a second mortgage on their homes and put down payments on two or three other properties. 

Whether they rent these out so that tenants pay the mortgage or they wait for an opportunity to sell for a profit, they control these assets, despite having only paid for a small part of the total value.