I get this question a lot, mostly from people who are up late at night watching info-mercials or watching the latest people on HGTV make a fortune. 

In our Charlotte NC metro market, the rental market has been soft right along with housing prices.  If you're a student of markets, you will note that they do run parallel to one another.  When folks are looking to be a landlord and add to a rental portfolio, there needs to be a slush fund available. 

For planning:  years 1 and 2 will most likely show a negative cash flow (you will have vacancies in between tenants plus your monthly rent may lag your mortgage if you didn't put a substantial amount down).  In year 3, with normal rent increases, you should breakeven.  By year 4, you should start seeing positive cash flow and beyond.

Timing is a factor as much as or moreso than the actual price of the unit.  If you are looking for a quick buck, keep looking for options out there.