Buying rental at a monthly loss

[Michael Osborne]

I am considering purchasing a property using 6 year financing at 5.99% interest. In this scenario I would be all in on a property at about $1000 a month. The property would rent for $750, so I would be out of pocket $250 a month. But after the 6 years I would own the property outright and without accounting for rent increases I would be clearing $625 a month. So I would have effectively paid $18k plus maintenance for a property that at year 7 is cashflowing $625+ a month. What are the major drawbacks of this approach?