Getting preapproved for an out of state mortgage?

My father and brother live in Portland, and they will need a new place to stay in a couple of months because their lease is up. I live in Illinois and will be moving to Portland in 1 year from now. Ideally I d like to buy a house in Portland for my dad and brother to live in until I move there. The loan would be in my name and my dad would cosign. The boys would make the mortgage payments until I moved out there next summer.
My question is, how do I go about getting preapproved for a loan that is out of state? And how can my dad cosign if he is there and I am here?

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