Q. I thought if I did the remodeling before I rented it out, it counts as a deduction. Is this correct?
A. No.
The remodel cost is added to your cost basis. In the case of the rental portion, that cost is depreciated over 27.5 years. Even "repairs" done, before renting it out, must be capitalized.
Q. Is there ever a scenario that when you remodel an investment that it counts as a deduction?
A. Simple answer: No. Small remodels done, after it is rented out, may qualify for the "safe harbor" deduction up to $2500. See https://www.irs.gov/businesses/small-businesses-self-employed/tangible-property-final-regulations
But, the increased cost basis reduces the amount of your capital gain, when you eventually sell.
