@VictoriaD75 's reply answers @JDM3 's question.
But, for other's reading this, the answer to all tax questions is: "it depends".
If the property was classified as investment property, as opposed to personal use property, prior to 2018, investment expenses were deductible, in the year occurred, as an itemized deduction, subject to the 2% of AGI threshold. That deduction is no longer allowed.
Alternatively, then and now, taxpayers can elect to capitalize (add it to your cost basis) the carrying costs of unimproved and nonproductive real property, real property under development or construction and personal property before its installation or use (Regs. Sec. 1.266-1(b)(1)). The election is made with the tax return by its due date, including extension, by attaching a statement. You cannot wait until you sell the property, but must make that election each year. Attach the statement to the return and write “Filed pursuant to section 301.9100-2” on the statement. You may add the carrying costs, incurred in the year of sale, to your cost basis.
Mortgage interest is only deductible to the extent of other investment income and not subject to the 2% of AGI rule, but can be capitalized. You cannot amend prior year returns to claim capitalization.
