I’d worry less about choosing a target yield yet and more about validating the description and rent. Phoenix and “coastal home” do not naturally match, so clarify exactly what is being sold and whether any additional community charges apply. Then get current insurance and tax estimates, compare...
Portability may not remove the need for a fresh affordability or property assessment, depending on the lender’s terms at the time. I would ask for the exact conditions in writing rather than assigning much value to the word itself.