How to evaluate what to pay for a rental property?

[Nick Mauren]

I am going to be buying a house soon to live in and in a year or two I would like to move out and then rent it.  I have a good idea of what I could charge for rent in the area but what is a good way to evaluate what I should pay for it?  I know that cash flow is important, but is there anything else to take into account for the purchase price?