Which mortgage should I take?

[Bienes Raices]

It looks like I have finally found a small bank that will approve a mortgage for me. I currently own my primary residence & rental free and clear. It's not approved yet, but here are the quotes I was given:

PRIMARY residence, worth $108,000 at 80% loan to value, the loan amount would be up to $86,400. At 4.375% the monthly payment would be $431.88.

RENTAL property worth $70,000 at 75% loan to value, the loan amount would be up to $52,500. At 4.875% the monthly payment would be $277.83.

These are for 30 year mortgages.

Obviously the rate on the primary residence is better, and I can potentially borrow more money. But I am not sure I want to live in this house forever (haven't decided yet). Will I be "trapped" in this house to keep the low rate? Is there a minimum number of years I should plan on staying in the primary residence if I take that loan to make it worthwhile? Or should I go with the rental property for the mortgage?

(the goal of getting the mortgage is to help buy another rental). Thanks.

[Loc R.]

If your goal is to buy more property, I would take the 1st loan.

That's going to be the cheapest and largest loan you'll be able to get, unless you intend on continuously moving primary residences.