Sauna / cold plunge - Tax Deductible for STR?

[masonmontero]

I started renting out my primary residence on Airbnb this year, 2025, and have already had it occupied for 50+ days that's generated $6,000+ of pre-tax income.

I'd like to know what the tax implications would be if I bought a sauna and cold plunge tub this year, 2025, for guests to use. I found this answer from ( @Tehaleonie / linked below) about hot-tubs but the OP had bought their hot-tub in the year before listing their property. If they are tax-deductible, can I deduct their entire cost if I never use them? How would I fill out next year's Schedule C?

Things to note, this is my primary residence currently and I plan on having it rented out around 100 days this year but in 2026, I plan on moving and making this a full-time STR. 

Deduction of hot tub if bought 1 year before renta 

[AnnetteB6]

If you are renting the whole house for certain periods of time as well as still living there when it is not rented, then the cost of the sauna/cold plunge would be prorated between rental days and personal days that the house was used for each.  It would not be reasonable to expect that it would be something only used by guests and never used personally in the case of renting the whole house.  

The sauna/cold plunge would be added to your return as an asset to be depreciated over time, or possibly written off as an expense if qualified (depending on the cost and other purchases you may have made for the rental).  

If you made the purchase after you fully converted the house to be a rental property, then there would not be any proration of the cost between personal/rental days.