Basically in the Your Home section you'll be entering two separate 1098's most likely. One for your primary residence, and another for your 2nd home. Be careful and read the small print on each screen, or you will most likely find yourself double-claiming things without realizing it.
You will not deal with the SCH E until you do your 2018 tax return next year. At that time, you will indicate that you converted the property from personal use to residential rental real estate. You should also keep all receipts for any and all property improvements you did, as you will be reporting them on the 2018 tax return. It does not matter that the property improvements were done in a prior year either. Property improvements add value to the property, regardless of when they are done.
You may claim the mortgage interest and property taxes on your Schedule A, until the property is rented.
You will add all the improvement on the property to the cost of the property and you will depreciate the property as you start renting it.
Also see the answer to the FAQ on what rental expense you can deduct as you start renting.