I bought a house in January 2024 and worked on rehabbing the whole year. My son moved into it in September 2024 but has paid no rent. What do I need to claim on taxes?

Nothing to enter about the house as a rental since no one paid any rent.   If you paid mortgage interest or property tax in 2024, enter the information from your 1098 from the lender.

Go to Federal> Deductions and Credits> Your Home to enter mortgage interest, property taxes, and mortgage insurance that you paid in 2024   You should have a 1098 from your mortgage lender that shows this information.  Lenders send these in January/early February or you may be able to import the 1098 from the lender’s website.