you need to factor into your equation:
- vacancy (over the long run you will eventually have weeks/months without rent
- repairs (you are responsible for most things, including big-ticket items)
- property management fees (you may/should decide this is the right thing to do, or you may end up hating this burden you have purchased).
your rent should be around 30% higher than your mortgage for you to be comfortable with covering the above IMO.