What is considered "living" in a duplex?

[Adam Mittermeier]

So I definitely like the idea of putting down 3-5% on a duplex instead of 20% on a single family house. So my question is, what is technically considered "establishing residence" in a duplex in Real estate terms to qualify for a loan with lower interest? Do you have to receive mail there? have a toothbrush at the house? What is the terms for that? 

The reason i ask is because i travel A LOT for work and am wondering how my residence would be established if im not really ever there.