Your understanding is essentially correct; depreciation does not begin until the rental property is placed in service. The property was not in service last year (2021) since it was not rented nor available for rent.
The expenses you can deduct for 2021 are limited to mortgage interest and real estate taxes (both subject to limitations) on Schedule A, assuming you itemize. The other expenses (such as utilities) are no longer deductible as miscellaneous itemized deductions after tax reform (the TCJA).
