绝大多数的市场 price－to－rent < 27.

How much is your annual rental income as compared to purchase price?  Let's say 4% (price to rent ratio of 25). 

and the depreciation of a strucutre (let's say 1/2 of the purchase price) is still nearly 2% of property value. 

So HALF of your rental income are washed out by depreciation. 

Next, your mortgage interest, property tax (usually more than 1% of property value) and other expenses would take a good chunk away from rental income.  

Usually you comes out negative with mortgage and depreciation.