Taxes/ question for accounants

[Gavin Wynn]

 Hey, This is a unique situation, I purchased my second property in June 2024, a single-family home that used to be a duplex, and is still zoned as a duplex ( remains 2 addresses). I am converting this back to a duplex, going to live in one half and rent out the other. Do I have to complete the separation of units by January 1st to write off half of my closing costs/other expenses?  Or can I still write off the closing cost in 2026 if I am not done with the separation by January 1st, 2025? This might be a stupid question but thanks in advance!