Renting out Primary home and Buying another

[Javier Galvan]

What are the Fannie Mae mortgage underwriting guidelines for Renting out Primary home and buying another primary home? 

I'm planning on 5% down conventional mortgage and having six months of PITI for rental property.

will I need to have a signed rental agreement in place to offset mortgage DTI or will I have to qualify for both mortgages.

Thank you.