How do contingency clauses work?

[James Theron Erwin III]

I'm looking for clarification on getting financing for a new home with the expectation that I will be renting my current home once I move out. I posted about a week ago asking about HMLs in order to get into the new property and was directed to contact some banks about getting more traditional financing. I have always heard that you can't count a property as a rental until it has been rented for 2 years. Does that mean just counting the income (cash flow, assuming there is any) or does that also include taking out the mortgage hit against my debt to income ratio?