50% Rule not working for me

[Andy H.]

Hi Everyone!  Newbie here...I am looking into Buy and Hold properties  and am trying to start with a single family house.  

I’ve been comparing House listing prices on Zillow and other websites with nearby rental rates for similar houses. When I do this, not a single property seems to meet the 50% rule in the DC suburbs (Maryland)...is that due to the location? The market? Or is it a problem with the way I am calculating things?  Maybe I just need more patience to find a deal?

Happy to be a part of this forum and to learn from you all.  Much thanks in advance.